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SCIENCE TEACHING 



BLACKIE & SON LIMITED 

50 Old Bailey, LONDON 
17 Stanhope Street, GLASGOW 

BLACKIE & SON (INDIA) LIMITED 
Warwick House, Fort Street, BOMBAY 

BLACKIE & SON (CANADA) LIMITED 
1 1 1 8 Bay Street, TORONTO 



SCIENCE TEACHING 

What it Was What it Is 
What it Might Be 



BY 



F. W. 

Formerly one of H.M. Inspectors of Secondary Schools 

Author of " Scientific Method, its Philosophical Basis and its 

Modes of Application ", "Science and Theology" 

"The Writing of Clear English", &c. 



BLACKIE & SON LIMITED 

LONDON AND GLASGOW 

1929 



Printed in Great Britain by Blackie & Son, Ltd., Glasgow 



To 
F. B. Stead 

(H.M. Chief Inspector of Secondary Schools) 
^Colleague and Friend for Twenty Years 



CRITICUS 

" Illud ferre non possum. Tu, quum me incognito assentiri vetes, 
idque turpissimum esse dicas et plenissimum temeritatis, tantum tibi 
arroges, ut exponas disciplinam sapientiae, naturam rerum omnium 
evolvas, officia describas, quam vitam ingrediar, definias: idemque 
etiam disputandi et intelligendi iudicium dicas te et artificium tradi- 
turum: perficies, ut ego, ista innumerabilia complectens, nusquam 
labar? nihil opiner? Quae tandem ea est disciplina, ad quam me 
deducas, si ab hac abstraxeris? Vereor, ne subarroganter facias, si 
dixeris tuam. Atqui ita dicas necesse est." 



AUCTOR 

" Si qua videbuntur chartis tibi, lector, in istis 

sive obscura nimis sive latina parum, 
non rneus est error: nocuit librarius illis 

dum properat versus adnumerare tibi. 
Quod si non ilium sed me peccasse putabis, 

tune ego te credam cordis habere nihil. 
* Ista tamen mala sunt.' Quasi nos manifesta negemus!" 

Haec mala sunt, sed tu non meliora facis." 



PREFACE 



A few years ago, a distinguished American educationist, 
who was on a visit to this country, told me that he had been 
reading an English hook on the teaching of science, and it had 
seemed to him that the writer had been devoting his energies 
to forging thunderbolts for hurling at those who refused to 
subscribe to the whole of the articles of a curiously narrow 
pedagogical creed. He said that it reminded him of the 
methods of certain theologians in his own country, and he 
asked me if I myself had adopted any sort of stereotyped 
procedure for assessing the value of a lesson in science. 

Thirty or thirty-five years ago, I might have felt a little 
uncertain of my answer. When I first became a headmaster, 
and had to assess the value of the teaching skill of my staff, 
I adopted a scheme, common enough in those days amongst 
Training College masters of method (as they were called), 
of awarding marks for each of a certain number of selected 
points class management, discipline, presentation of subject- 
matter, interest, lucidity, logic, form of questions, use of 
answers, success of experiments, use of experiments, use of 
experimental facts, use of hypotheses, method of establishing 
principles, general attitude towards theory, English, note- 
taking, and so on and in that way I was able to make a rough 
estimate of a teacher's skill. The scheme seemed to work 
well enough in the case of teachers who taught on fairly ortho- 
dox lines, but, when I began work as an inspector, I soon dis- 
covered that the scheme not infrequently failed, successful 
teaching methods often differing radically. Sometimes a 
teacher would offend against almost every accepted Training 
College precept, and yet give a strikingly successful lesson. 

vii 



vriii SCIENCE TEACHING 

Despite his entirely unconventional methods, he might have 
a gift of putting things so lucidly and in such an interesting 
manner, and his personality might be so dominating, that the 
boys would be simply carried away. The experienced critic 
soon finds it necessary to abandon all attempts at assessing 
values mechanically, though certain criteria will always be 
borne carefully in mind. 

There is general agreement amongst those of us who have 
spent our lives as critics of teaching methods that the very 
last thing we desire to find in a teacher is that he has sur- 
rendered his own individuality and teaches in accordance with 
some other person's scheme of hard and fast rules. 

Suppose that a teacher, who has to give a lesson on some 
particular topic, first forms in his own mind a perfectly clear 
and vivid picture of the subject, and then, in giving the lesson, 
succeeds by some means in transferring the picture to the minds 
of his pupils, who are then able to see it as clearly and vividly 
as the teacher himself does. Suppose, further, that we test the 
pupils and find that they have not only got hold of the facts 
but understand them perfectly. Even if that teacher's methods 
were entirely opposed to methods generally recognized, can 
we justly say that the teacher would have clone better if he 
had set to w r ork in a more orthodox way? 

Perhaps the lesson has taken the form of a lecture. Some 
critics would then urge that although the pupils may have 
obtained a number of new facts, have understood the facts 
perfectly, and have made them a permanent possession, yet 
such a lesson is necessarily a failure because it has made no 
provision for a formal training, and that a particular perhaps 
a unique kind of formal training is the one claim that science 
can make for inclusion in the school curriculum. 

But in making exclusive claims for science as a subject 
for training the mind, we are on very dangerous ground. Critics 
who will listen dispassionately to equally able specialist teachers 
giving lessons in, respectively, classics, mathematics, history, 
knd science, will be forced to admit that, as far as mere intel- 
lectual training is concerned, it is exceedingly difficult to 



PREFACE ix 

assign a preferential award to any particular one. The only 
exclusive elaim of science is that it is dealing with facts un- 
tingeu with any sort of human prejudice (unfortunately, this 
does not apply to the hypotheses of science!): learners can 
thus be taught to form an objective judgment. But this very 
source of strength is also a source of weakness. A training in 
science can make no provision for an analysis of human motives 
or of any sort of emotional experience; and thus it does not 
prepare its learners to understand some of the greatest problems 
of life. And, after all, it is a people's literature, not their 
science, that depicts their character their strivings and their 
failings, their laughter and their tears, and all those things 
that rouse to action. 

The principal subjects taught in school are one and all 
intended to provide a mental training, each of them of its 
own kind, all in their way equally valuable. When it comes 
to a struggle with difficulties, the student of classics and the 
student of mathematics are at least as hard put to it as the 
student of science. The great claim of science for a place in 
the school curriculum is its provision of new knowledge, 
knowledge which is ever increasing, knowledge which is driv- 
ing the world ahead, knowledge which it behoves every citizen 
to possess. 

To urge this necessity for the dissemination of knowledge 
is not to underrate the value of teaching as an art. But the 
art of teaching cannot be analysed and reduced to rules. The 
art is the creation of a teacher as an artist, " varying with his 
gifts, fed by his knowledge, enriched by his qualities, expressing 
his own unique personality ". The teacher does not shape 
his material to his will, as an artist does who works in clay. 
He works on human lives which are themselves an active force 
in, the process. Hence the art of teaching is more complex, 
more baffling, more elusive, than any other art, and none of 
us need feel ashamed that we are unable to reduce it to prin- 
ciples and state its canons. 

But, if it is nothing else, the art of teaching is, at least 
in skilful hands, dynamic, intensive, even aggressive. The 



x SCIENCE TEACHING 

mere pabulum the teacher uses for his purpose, science, litera- 
ture, or what not, matters little. The teacher who Understands 
his work will make his own subject intellectually exacting 
be the subject what it may. 

It has been seriously said that Britain might still retain 
her leading place amongst the nations of the world if all her 
rulers were men of science. Such a statement is only provo- 
cative of ribaldry. Would the penetration of such men into 
human motives be clearer? would their judgments be more 
impartial? would their ability to \veigh evidence be greater? 
Nevertheless, it would be better for us all if our rulers had a 
deeper knowledge of science, if they more clearly understood 
its applications, and if they were thus able to give the people 
a clearer orientation of the social forces contributing to our 
environment and moulding the future. Indeed, our rulers 
ought to be equipped in such a way as to be able actually to 
discover such forces, and some knowledge of science and some 
training in scientific method are essential for such discernment. 

A recognized leader of political thought recently described 
inoculation as unclean! A medical man recently giving evidence 
before a salaried judicial functionary said, " the woman had 
an aneurism in the sub-clavian artery ", a statement expressed 
in terms so simple and accurate as to be unexceptionable. But 
the medical man was promptly rebuked by the functionary for 
" indulging in scientific jargon "! Ill-informed politicians may 
still win for themselves a measure of esteem from the ill- 
informed sections of their constituents; ill-educated men may 
still be jockeyed into important official positions. 

But an eminent man of science went a little too far when 
recently he said, " at present the policy of most states is framed 
by politicians, carried out by civil servants, and interpreted 
by journalists, all equally ignorant of science ". Of journalists, 
I have no knowledge. Politicians as a class certainly do seem 
to be ignorant of science, but in every party there are states- 
men (Lord Balfour is one, Lord Haldane was another) whose 
wide and, accurate knowledge of science commands* respect. 



PREFACE xi 

As for civil servants, I happen to know that within their ranks 
is a large number of men with high scientific attainments. 
Whilst it is quite true that there is a general ignorance of 
science amongst the more responsible classes of the community, 
exaggerated statements from men of eminence are not likely 
to advance the cause that such men have so warmly at heart. 
There can be no doubt that the science teacher's real battle 
is concerned at least as much with the dissemination of know- 
ledge as with the training of the intellect. Science teachers 
must cease to look at their several subjects so much from the 
inside. They must try to appreciate the unity of purpose of 
the whole range of scientific study, and the impacts of this 
study upon the common stock of ideas. They must break 
with the bad tradition of serving up year after year the same 
twopenny-worth of weighing and measuring that poor little 
miniature of a university dish, not even garnished to conceal 
the beggarly fare it contains. They must broaden the basis 
of their teaching, particularly by the inclusion of biology. 
They must extend their pupils' scientific horizon. They must 
give up the idea that, if they give a lesson on some small topic 
of science by methods which will win the warm approval of 
the doctrinaire critic, they are therefore discharging effectively 
their main function as science teachers. The teaching of science 
is a much bigger thing than the devising of means of giving 
satisfaction to critics of the minutiae of laboratory procedure. 
A laboratory is not a place either for the mechanical repetitions 
of a cloistered cell or for the dusty ritual of an antiquary's den. 
At present, biology receives such little attention that several 
chapters of the book are devoted to considering its possible 
developments in school science courses. No school will be 
able to find time for the whole of the work outlined, and any 
school which attempts anything like a complete biological 
course will probably be compelled to drop a good deal of the 
usual physics and chemistry, with the possible consequence 

* For instance, three of my old colleagues at the Board of Education were Fellow* 
of the Royal Society, and many others had obtained the highest Distinction in science 
that their universities could offer them. And I believe it is a fact that science is no 
less well represented in the other Government departments. 



xii SCIENCE TEACHING 

of weakening foundations generally. Much will depend upon 
the amount of time that can be given up to science. The 
present neglect of biology is all the more lamentable seeing 
that there is now a world- wide recognition of the fundamental 
importance of an expert knowledge of plant physiology and 
plant pathology (to mention only one aspect of biology). 
Within the next few years there is likely to be a far greater 
demand for trained biologists than our schools and universities 
can possibly meet. Whose is the fault? 

It is in the Sixth Form where new teaching experiments 
may be freely tried. By that time pupils will, presumably, 
have been well trained in essentials, especially in the essentials 
of scientific method, and teaching methods may then become 
much more varied and much freer. A good deal of attention 
has therefore been devoted, in later chapters, to possible 
Sixth Form work on new lines. The needs of the Higher Certi- 
ficate examination have, of course, to be borne in mind, but, 
if science teachers will only agree amongst themselves as to 
the scope and extent that Sixth Form work might best assume, 
they will probably enlist the ready sympathy of examination 
authorities. 

In some of the chapters dealing with subjects not often 
taught, rather more than mere running comments on methods 
have been given: a certain amount of subject-matter itself 
has been included, always in a condensed form, just enough to 
indicate what to look for in the textbooks and what general 
sequence to follow. 

Any merit that this book may possess must be ascribed to 
the many hundreds of science teachers whose work I have 
been privileged to see. I have been present at something like 
1000 lessons a year for over 30 years, and naturally there have 
been occasions when the lessons were not an unqualified suc- 
cess. Rarely, however, have I failed to discover in a lesson 
something worth remembering, and I hope that the results of 
this gleaning find garnering, as here presented, will help to 
make the work of beginners a little more fruitful. 



CONTENTS 



PART I 
SOME PRINCIPLES OF SCIENCE TEACHING 

CHAPTER I 
THE TEACHER: HIS KNOWLEDGE AND HIS TRAINING 

Page 

The Marks of a Successful Science Teacher 3 

Academic Knowledge --------4 

Training ..........7 

CHAPTER II 
THE PURPOSE OF SCIENCE TEACHING 

The Specific Claims of Science ...... 9 

The Cultural Value of Science ------ 9 

The Training Value of Science - - - - - -n 

Formal Training versus Cultural Value - - - - 13 

CHAPTER III 
METHODS 

Methods of By- gone Ages - - - - - - -14 

Science Teaching from 1867 - - -- - , *5 

The Methods of Forty Years Ago ,-17 

xiii 



xiv SCIENCE TEACHING 

Page 

The " Heuristic " Method - - - - - 20 

Lecture-room and Laboratory - - - - 28 

Lecture-room versus Laboratory - - - - - - v 30 

The Historical Method 31 

Huxley's Method - - .. - - . . -33 

The " Concentric " Method 34 

Present-day Tendencies .......36 

General Remarks on Method - - - - - -38 



CHAPTER IV 
SELF-TRAINING 

Hints to the Beginner - - - - - - - -41 

Books to Read and How to Read Them ----- 42 



CHAPTER V 
LABORATORY DIRECTIONS, BAD AND GOOD 

Directions open to Criticism -------47 

Directions which may be regarded as Models - - - 52 

CHAPTER VI 
A COMMON CAUSE OF FAILURE 

First Illustrative Example: Boyle's Law ----- 58 
Second Illustrative Example: The Law of Charles - - 61 

CHAPTER VII 
THE CONTENT OF THE NORMAL SCIENCE COIJRSE 

The Course up to School Certificate Stage .... 66 
Girls' Schools 7 

Sixth Form Science - - - - - - - -72 

Non-specialist Sixths - - - - - - - -75 

Time Allowance ---------76 

Directed Reading --.------78 



CONTENTS xv 

CHAPTER VIII 
LOWER FORM SCIENCE 

Page 
Nature Study --------- 79 

Elementary Physical Science - - - - -.- -82 

CHAPTER IX 
SYLLABUSES AND SCHEDULES OF WORK 

Examiners' Syllabuses and Teachers' Syllabuses 86 

Sir A. D. Hall's Three-years' Course ----- 87 

"' Science for All " 89 

'" Educational Pamphlet 17"- - - - - - -90 

The Preparation of a Teaching Syllabus - - - - 9 1 

A Teaching Syllabus in Chemistry 92 

An Approach to Botany, Experimentally ----- 102 

CHAPTER X 
SCIENCE TEACHERS AS TEACHERS OF ENGLISH 

Is the Technical Terminology of Science Necessary? - - 107 

'Simplicity of Expression in Science Teaching - 109 

Note-making and Note-taking - - - - - - H3 



PART II 

THE DIFFERENT SUBJECTS 
OF INSTRUCTION 

CHAPTER^XI 
MECHANICS 

\Vhy must Mechanics be included in any Science Course? - - 119 

The Teacher of Mechanics - - - - - - -121 

The First Stage in the Teaching of Mechanics - - -123 

The Second Stage - - - - - - - -125 

Hydrostatics - - - - - - - - -127 

Some Snags - - - - -- - - -128 

Units - - - - - - - - - -132 



xvi SCIENCE TEACHING 

CHAPTER XII 
PHYSICS 

Page 

The Normal Course: General Considerations - - - 134 

Present-day Developments in Electrical Courses - - 137 

The Necessity for a Greater Width in a Physics Course - - 140 
Practical Physics - - - - - - - - -142 

More Snags ......... 143 

Tendencies of Modern Physics: Should Schools ignore them? - 153 
A Lesson on X-rays - - - - - - - -154 

CHAPTER XIII 
CHEMISTRY 

In Close Touch with the World Around 156 

Organic Chemistry - - - - - - - -158 

Practical Work in Organic and Physical Chemistry - - - 161 
Occasional Re-grouping of Topics - - - - - -162 

Chemical Theory - - - - - - - - -163 

Still more Snags 169 

Logical or Psychological Order? - - - - - -174 

The History of Chemistry 175 

Text- books and New Books - - - - - - -176 

Laboratory First Aid - - - - - - - -177 

Terminology - - - - - - - - -178 

CHAPTER XIV 
BIOLOGY 

The Neglect of Biological Teaching 179 

Main Principles of Biological Instruction - - - - 181 

Biology a Difficult Subject to Teach 182 

Biology as a Group of Allied Studies - - - - 184 

CHAPTER XV 

BIOLOGICAL CLASSIFICATION AND 
TERMINOLOGY 

Main Principles of Biological Classification - - - - 186 
Nomenclature - - - - - - - - -188 

Classification in School Work t - 188 

Biological, Terminology - - - - - - -189 

(E72) 



CONTENTS xvii 

CHAPTER XVI 
BOTANY 

Page 

Experiments Essential from the Outset - - - - 190 

The Earlier Work in Botany - - - - - - -191 

Sixth Form Work - - - - - - - -193 

School Gardens - - - - - - - -194 

Rambles and Excursions - - - - - - -195 

By-ways in Botany - - - - - - - -196 

Final Snags - - - - - - - - -197 

CHAPTER XVII 
ZOOLOGY 

Function rather than Form ------- 204 

Early Observational Work ------- 207 

Further Work - -211 

Laboratory Procedure: The Microscope - - - - -212 
Collections of Animals - - - - - - -'- 214 



CHAPTER XVIII 
HUMAN PHYSIOLOGY 

To what Extent is the Subject Necessary? - - - 215 

Topics for Special Consideration - - - - - -216 

Bio-chemistry - - - - - - - - -218 

Actinotherapy - - - - - - - - - 222 

CHAPTER XIX 
EMBRYOLOGY 

Why Embryology should be Taught ----- 223 
The Basic Facts to be Taught .-..-- 224 

Practical Work 225 

Mitosis - - - - 227 

Animals and Plants -------- 228 

The " Recapitulation " Theory 228 

Human Embryology - - - - - - - -229 

Material and Books - - -- - -*- - 229 

'2 



xviii SCIENCE TEACHING 

CHAPTER XX 
HEREDITY 

Page 

The Basic Facts for the Pupil 230 

Hypotheses of Heredity - - - - - - -231 

Main Principles now Generally Recognized - ... 238 

CHAPTER XXI 
EVOLUTION 

The Great Range of the Subject 243 

A Suggested Sequence of Topics ------ 244 

The Biologist's Genealogical Tree ------ 250 



CHAPTER XXII 
GEOLOGY AND PAL/EONTOLOGY 

The Geology Commonly Taught - - - - - -253 

Why some Knowledge of Palaeontology is Necessary - - - 255 
Suggested Topics for Inclusion in a School Course - - 255 

The Descent of Man -------- 264 



CHAPTER XXIII 

BACTERIOLOGY 

The Present Importance of the Subject 266 

CHAPTER XXIV 
HYGIENE 

Hygiene as Taught Forty Years Ago ----- 276 
The Kind of Teaching advisable To-day - - - - 278 

The Foundations of Hygiene - - - - - - --281 



CONTENTS xix 

CHAPTER XXV 
BIOLOGICAL BY-WAYS 

Page 
Occasional Work for Abler Boys ------ 282 

Special Points suggested for Consideration .... 282 

CHAPTER XXVI 
ASTRONOMY 

The Astronomy usually Taught ------ 284 

A More Serious Course of Astronomy ----- 287 

Practical Work --------- 290 

Sixth Form Work -------- 291 

Topics for Lectures -------- 294 

CHAPTER XXVII 
SCIENCE IN RURAL SCHOOLS 

The Kind of Work that is Advisable 302 

Drawing up a Course: Some Principles ----- 303 

Suggested Outline Courses ------- 304 

Out-of-door Practical Work ------- 306 

Other Supplementary and Complementary Work - 307 

Sixth Form Work --....._ 308 

CHAPTER XXVIII 
DOMESTIC SCIENCE 

" Science " or " Craft " ....... 308 

Cleaning Agents and Operations - - - - - -311 

The Study of Proteins - - - - - - - -314 

CHAPTER XXIX 
METEOROLOGY AND WEATHER FORECASTING 

The Newer Aspects of the Subject - - - - - -317 

The Teaching of the Subject - - 324 

Forecasting - -*- - 325 

Concluding Remarks - - - - - - - . 326 



xx SCIENCE TEACHING 



PART III 

EXTENDED CONSIDERATIONS FOR 
SIXTH FORMS 

CHAPTER XXX 
SIXTH FORM WORK AND ITS CRITICS 

Page 
Sixth Form Work and its Critics 329 

CHAPTER XXXI 
THE STRUCTURE OF THE ATOM 

Astronomical Considerations ------- 333 

The Periodic Law - - - - - - - -334 

Radioactivity - - - - - - - - -334 

^Etherial Radiation and Wave Measurement - - - - 33 

The Hydrogen Spectrum - - - - - - -336 

The Balmer Formula - - - - - - - -337 

The Grouping of the Different Hydrogen Series - - - 339 
Bohr's Interpretations - - - - - - - -341 

Energy Considerations -------- 345 

Moseley's Discovery - - - - - - - "347 

A Necessary Warning -------- 348 



CHAPTER XXXII 
RELATIVITY 

Why Beginners find Relativity so Difficult .... 349 

Before Einstein - - - - - - - - -35 

Einstein and Afterwards - - - - - - -352 

The Special Theory of Relativity -- - - -352 

The General Theory of Relativity - - - - - -353 

Tests of the New Law of Gravitation - - -357 

The Relativity of Simultaneity 357 

Unsolved Relativity Problems ,- 372 

Another Warning - - - - - - - -373 



CONTENTS xxi 

CHAPTER XXXIII 
THE VERY GREAT AND THE VERY SMALL 

Page 
The Very Great and the Very Small - 373 

CHAPTER XXXIV 
THE HISTORY OF SCIENCE 

Why the History of Science should be Taught - 378 

General Lessons on Earlier Science - .... 379 

Lessons on the History of Particular Subjects - - - 380 

The Personalities of the Great Workers - - - - - 380 

Dates 382 

CHAPTER XXXV 
RESEARCH: ITS SIGNIFICANCE AND IMPORTANCE 

Research: Its Significance and Importance - ... 383 

CHAPTER XXXVI 
THE PHILOSOPHIC FOUNDATIONS OF SCIENCE 

First Notions of Philosophy ------- 386 

Induction and Hypothesis - - - - - - -389 

Should the older Hypotheses be Discarded? - - - -391 

Is Mathematical Reasoning Trustworthy? - ... 393 

Non-demonstrable " Proofs " - - - - - - 394 

An Outline Lesson on Inference - - - - - -3 98 

CHAPTER XXXVII 

SCIENCE AND HUMANISM 

Sciencfe and Humanism ... - - . 400 



xxii SCIENCE TEACHING 

PART IV 
ACCOMMODATION AND EQUIPMENT 

CHAPTER XXXVIII 
LABORATORIES AND EQUIPMENT 

Page 

Laboratory Accommodation Generally ----- 407 
Lecture-rooms --------- 409 

Preparation- rooms, Balance-rooms, &c. ----- 410 

Chemical Laboratories - - - - - - - -410 

Physical Laboratories - - - - - - - -413 

Biological Laboratories - - - - - - - -415 

The School Observatory - - - - - - -4^5 

Apparatus and Equipment - - - - - - -416 

The Workshop 421 

CHAPTER XXXIX 

SCIENCE LIBRARIES 

Science Libraries --------- 422 

APPENDIX 

QUESTIONNAIRES FOR PUPILS AND FOR TEACHERS 

A Questionnaire for Boys Leaving School ... - 427 

A Questionnaire on General Science ----- 428 
A Questionnaire on Methods of Teaching - 430 

INDEX .-- 433^ 



PART I 

SOME PRINCIPLES OF SCIENCE 
TEACHING 

The chapters of this section of the book refer mainly to 
methods methods which are known to be sound and methods 
which are known to be otherwise. 



CHAPTER I 

The Teacher: his Knowledge and 
his Training 

The Marks of a Successful Science Teacher 

What are the marks of a successful science teacher? He 
knows his own special subject through and through, he is 
widely read in other branches of science, he knows how to 
teach, he knows how to teach science,* he is able to express 
himself lucidly, he is skilful in manipulation, he is resourceful 
both at the demonstration table and in the laboratory, he is 
a logician to his finger-tips, he is something of a philosopher, 
and he is so far an historian that he can sit down with a crowd 
of boys and talk to them about the personal equations, the 
lives, and the work of such geniuses as Galileo, Newton, 
Faraday, and Darwin. More than all this, he is an enthusiast, 
full of faith in his own particular work. 

He may have first-rate laboratories and equipment, a 
generous time-allowance, and an ideal syllabus, but, unless 
he really knows how to teach and is keen on his work, success 
will not come his way. On the other hand, if he is keen and 
well-informed, he may succeed in spite of discouragement and 
poor equipment. 

It is the man that counts. All obstacles he pushes aside. 

* I have differentiated between " teaching " and " the teaching of science ". 
The book does not set out to give an exposition on the art of teaching in the broader 
sense. Nothing, for instance, is said about discipline, and very little about the rfrt 
of questioning, or about a score other things that every teacher ought to know, 
whatever his subject may happen to be. There are at least half a dozen helpful 
handbooks dealing with all such points, and Ward and Roscoe's Approach to 
Teaching, the newest, is full of hints of the greatest value, hpth to beginners and 
to teachers of experience. It contains a final chapter of useful suggestions for a 
teacher's library. 

3 



SCIENCE TEACHING 



Academic Knowledge 

What academic knowledge may reasonably be expected 
from a science teacher? A Cambridge science degree admittedly 
stands first. There are advantages at Cambridge not to be 
had at any other university in the world. During four years 
there, a man * will have taken up three or four different 
subjects, specializing in one. At Oxford (where science is 
at last creeping ahead, though its taps on the door of the 
temple of the " Greats " are still too gentle to be heard 
within), most of the time will be devoted to a single subject. 
At London and the newer universities, one principal subject 
and one subsidiary subject are most likely to form the course 
taken up (it is assumed that the man is reading for an 
Honours degree). Is the knowledge thus acquired enough for 
teaching purposes? 

Emphatically the answer is in the negative. The university 
courses have not been designed primarily for teachers but for 
science specialists chemists, engineers, biologistr, and others. 
The university provides no special training in scientific method; 
it assumes, rightly or wrongly, that that has been provided at 
school. The work done is of necessity largely technical, and 
in that sense travels beyond the boundaries of school work. 
A university rightly considers that one of its main functions is 
to prepare a man for the continued study of his subject through- 
out his life, to help him wrestle with the intellectual difficulties 
arising out of that particular branch of knowledge, and thus 
to teach him how to dig down to the foundations of any kindred 
branch of knowledge that in future may interest him. 

On the other hand, much of the work which is necessary 
for schools is often not included in the course selected for a 
university degree. A degree may be taken, for instance, mainly 
in chemistry, and the man be wholly ignorant of biology and 
almost ignorant of physics. There are instances of men who 
have taken a " science " degree in mathematics, logic, and 

* I apologize to science mistresses for adopting this unsatisfactory translation 
of homo sapiens.' 



THE TEACHER 5 

psychology, and have never lighted a bunsen or handled a 
test-tube in their lives. There are other instances of men who 
as private students have taken a science degree in chemistry 
and physics and have spent less than six months in laboratory 
work. Graduates of these classes are seriously handicapped 
if they take up science teaching, for they have to settle down 
to a great deal of drudgery, rarely very fruitful in its results, 
in order to equip themselves adequately for the professional 
work they have taken in hand. 

Admittedly the necessary approach to science in school is 
fundamentally different from that of the university. University 
teachers naturally assume that their students are capable of 
taking in " lectures " and do not require " lessons ": that 
theoretical courses and laboratory courses, though proceeding 
more or less collaterally, are not necessarily interrelated step 
by step as in schools. A young science master sometimes doles 
out to his boys the petrifying stuff from note-books compiled 
at his university lectures, with barren results as he soon dis- 
covers . 

But the value of the highly specialized work done in 
university courses must not be underrated. Unless a science 
teacher has carefully examined both the foundations and the 
superstructure of at least one subject of science, and has 
wrestled with its real difficulties, his respect for his work is 
not likely to be great; and only then has he the legitimate 
right to sit side by side with the classical scholar and with the 
trained mathematician. 

A science teacher can hardly claim to be well equipped 
for his work before the age of 30 or 35. The trifle that he 
reads during the three or four years at the university counts 
for something, but what he reads during the ten or fifteen 
years afterwards counts for very much more. A science teacher 
ought to know something, and know that something well, of 
every main branch of science; and at least a full year of leisure 
time must be given up to a new branch before its outlines can 
be mastered and before the foundations on which it rests can 
be fully examined. 



6 SCIENCE TEACHING 

Science teachers who have been reading science for thirty 
or more years have told me how sadly out of date they feel 
themselves to be because of the impossibility of keeping in 
touch with the ever-increasing advances in the subject. Men 
who have taken up classics, or modern languages, or history, 
or mathematics, are in a rather different position. At the 
university they covered much of the ground in their subject 
fairly exhaustively, and they have since been able to keep in 
touch with research and new knowledge. But science has 
become such a vast subject, and in its rapid development it 
so easily outstrips all other subjects, that in a period of three 
or four years it is hopeless to try to cope with more than a 
selected corner of it. The remainder must come later, though 
alas! the greater part of it is likely to remain a sealed book 
even to the elect. 

It is not merely necessary to take up new subjects, but 
to broaden and deepen one's own special subject. Consider, 
for example, how relatively little ground in chemistry can be 
covered in a university course. Much subsequent time is 
necessary for following up its manifold new departures and its 
ramifications into industry, physiology, and agriculture. It 
is not that the teacher may require for his daily work in the 
lecture-room and laboratory a knowledge of recent research 
(though for present-day Sixth Form work a science teacher 
must be abreast of the times); it is rather that a stale teacher is 
an unenlightened teacher. A stale teacher may not hark back 
quite so tar as the age of phlogiston, but he is ever in danger 
of using hypotheses that had for a time been provisionally 
pressed into service but have since been thrown on the rubbish 
heap. 

When a teacher's knowledge of science is confined to that 
of his university course, he has no claim to be made head of 
his department. He is unable to organize the work of his 
department as a whole, to supervise the work of his younger 
colleagues, to advise on the teaching of other science subjects, 
or, in short, to do more than when he was an irresponsible 
junior. 



THE TEACHER 7 

There is no excuse whatever for ignorance of the bare 
fundamentals of the main branches of science. Some years 
ago a 'science mistress who had taken a First in Botany Finals 
and who was a first-rate microscopist was giving a lesson on 
the barometer to a middle form (she was working single- 
handed), and a child asked, " Why does the barometer read 
the same in the laboratory as in the playground, seeing that 
outside there is a much higher column of air on the mercury?" 
Within the hearing of an inspector the mistress replied, " That 
is one of those things that even the cleverest men of science 
have never been able to discover "! That such a teacher 
should have been given a degree at all is positively immoral. 
Her answer showed that she did not know the ABC of elemen- 
tary science. 

Let the botany teacher remember that he must have a 
sound knowledge of chemistry and of elementary physics; the 
chemistry teacher, a sound knowledge of physics; the physics 
teacher, a sound knowledge of mechanics and mathematics; 
the mathematics teacher, at least an elementary knowledge of 
the philosophical foundations of his subject. 

In short: a university course in science is just a preparation 
for the serious reading of the years to come. 

Training 

Nobody denies that a medical man or an engineer must 
be trained, for each of them has to acquire a knowledge of an 
art based on definitely established scientific principles. When 
people deny that a teacher need be trained, do they mean that 
teaching is merely a labourer's job? Do they deny it the rank 
of an art with its own definitely established principles? Is there 
anything for a beginner to learn from the experienced successful 
teacher? If so, what? and how should he learn it? 

If he is lucky enough to spend a year at a training college 
where the principal himself is a man of science and a recog- 
nized authority on science teaching, or where at least the head 
of the * department has been able to obtain similar public 



8 SCIENCE TEACHING 

recognition, he will probably receive the best training possible. 
Failing that, a post-graduate student-teachership at*one of the 
great secondary schools where the science teaching is of recog- 
nized excellence, where the headmaster and the science staff 
will give a warm welcome to the novice, is perhaps the best, 
especially if, during the latter half of the year, lectures at 
university training departments can be attended. Of the 
twenty most successful teachers I have known, eleven were 
untrained, five were trained at a training college, and four 
at secondary schools. But the eleven were exceptionally 
gifted men and women, the sort of people who would have 
succeeded in any walk of life, no matter what difficulties they 
encountered. 

Science teachers who have successfully undertaken a certain 
amount of research as part of their university course have 
probably obtained a clearer insight into scientific method than 
they could have obtained from most courses of training college 
lectures. In any circumstances, a training in the principles 
of scientific method is an essential part of the training of all 
science teachers. Some knowledge of the history and philosophy 
of science is also indispensable. Such knowledge will enable 
teachers to assess more correctly the true value of science 
as an educational instrument; it will make them more severely 
critical of loose reasoning; it will provoke them to be more 
insistent on accuracy of thought in their pupils. 



THE PURPOSE OF SCIENCE TEACHING 9 

CHAPTER II 

The Purpose of Science Teaching 

The Specific Claims of Science 

The two principal claims of science for inclusion in a school 
course are so well known as to be almost commonplace. In 
the first place, the claim is made that it affords an unrivalled 
intellectual training, and teaches the learner to reason from 
definitely^ ascertained facts and to form an objective judgment; 
in the second place, that by its discoveries science is now making 
such great contributions to the prosperity of the human race, 
and. is adding so rapidly to the sum of our knowledge, that the 
minds of those who are unversed in at least its main principles 
are, if not half barren, certainly imperfectly cultivated. 

But it is difficult to maintain the first claim as the claim 
of science exclusively. If properly taught, classics, mathe- 
matics, or history provides an intellectual training not inferior 
to that provided by science; and classics and history have 
this advantage over science, that they take account of motive 
and action. It is true that science takes account of the analogous 
relation, cause and effect, but this relation is a much simpler 
relation; and thus, for the purpose of searching out the con- 
nexion between marshalled arrays of facts, science has the 
advantage of comparative simplicity. But unless science in- 
cludes within its scope some consideration of human relations 
and interests, its priority of claim as an educational instrument 
will not remain uncontested. 

The Cultural Value of Science 

Now that science enters so widely and so intimately into 
every department of life, especially in all questions relating to 
health and well-being, it is important that the community 
should have a general knowledge of its scope arid aims, of the 



io SCIENCE TEACHING 

mode in which it envisages and attacks its problems, and of 
scientific method generally. It is, however, beyortli question 
that it should be a general knowledge on broad lirfes: a 
specialized training in some highly technical branch of science 
is neither necessary nor desirable. But the general knowledge 
must be an accurate knowledge, a closely reasoned-out know- 
ledge, built up on a basis of undisputed facts. 

As a means of culture, the history of scientific discovery 
opens up to the imagination great pictures of the work of 
great men, thereby placing science in the front rank of 
humanistic studies. A knowledge of the methods of obser- 
vation and experiment in the different branches of science 
helps to develop a logical mind, a critical judgment, and a 
capacity for methodical organization; while a knowledge of 
the great questions with which science as a whole is concerned 
fosters the broad outlook which is essential for the successful 
solution of the problems of life. 

Is our present science teaching designed to meet these ends? 
Is there not some confusion between instruction in science 
and instruction in scientific technique? Are we not tending 
to teach science for specialists instead of science for citizenship? 

It may be urged that a change in the direction of making 
our school science courses more general will result in giving 
children a mere smattering of a subject. But are children 
being given more than a mere smattering now? 

Assuredly any science course should not only train pupils 
to weigh and interpret observed experimental evidence, but 
should also make them acquainted with the broad outlines of 
great scientific principles, with the way in which these prin- 
ciples are exemplified in familiar phenomena, and with their 
applications to the service of man. The two things should be 
recognized, and school courses framed accordingly. 

But the tendency of recent years has been to over-emphasize 
the formal training, and to attempt to propitiate caustic critics 
by making great sacrifices on the altar of weighing and measur- 
ing; in short, to underrate the value of work at the demon- 
stration table. 



THE PURPOSE OF SCIENCE TEACHING n 

There is a certain body of scientific knowledge and a certain 
number of scientific ideas with which everybody ought to be 
familiar. These ideas permeate the whole atmosphere of 
common thought at its higher levels, and provide the basis of 
most forms of human activity. Gifted men well versed in other 
branches of knowledge, when dealing with certain aspects of 
practical affairs, are apt, apparently from the sheer absence 
of a common standpoint, to remain incapable either of appre- 
hending the train of reasoning adopted by scientific men, or 
of seeing the importance of certain classes of evidence which 
it is absolutely necessary to w r eigh before a course of action 
can be rightly decided upon. 

The ritual of the laboratory must not be confused with 
the spirit of science. The spirit of science cannot be weighed 
and measured, even if weighing and measuring are necessary 
for tracking it down. It is not enough to track it down, it 
must be captured; and not infrequently it evades capture 
because the reason is lethargic and the imagination dull. 

The bed-rock facts of science are, of course, of fundamental 
importance, but, as an introduction to the teaching of science, 
they are certainly rather unexciting to children. In the early 
stages, facts which are not given a background of interest 
repel rather than attract. A first-year school course, designed 
to give a grounding in elementary science, often consists of 
colourless and uninspiring data. 

The Training Value of Science 

That a formal training in the methods of science is necessary 
will be admitted by all, and this formal training must be 
exacting, otherwise it will be of no avail. But a thread of 
interest of some kind should always run through the earlier 
general courses of instruction. Sometimes that thread of 
interest may be historical, the teaching being directed, in some 
measure, to giving general ideas of the development of science 
in the service of mankind. The long and patient struggle 
associated with the great names in science, the long series of 

(E72) 3 



12 SCIENCE TEACHING 

lucky accidents, of bold hypotheses, of painstaking studies, 
the failures and the disappointments as well as th6 successes, 
are the materials with which the imagination of the pupil 
may be kindled. Treated in this way, a science course may 
leave on the pupil's mind a lasting and vivid picture of human 
endeavour, throwing light on the past and the present, and 
giving glimpses of possible achievements in the future. 

But the formal training should have as its ultimate goal 
the making of " a cold logic engine ", as Huxley phrased it: 
a training in observation, in the garnering of facts, in the 
sifting of evidence, in the framing of hypotheses, in the scrutiny 
of hypotheses in the light of new facts, in the training of the 
impersonal judgment; in short, the training will be an initiation 
into the whole procedure of making a methodical purposeful 
quest amongst a tangle of physical happenings. If a boy is 
properly trained, the desire for discriminating evidence will 
become a predominating factor in his mental outlook. 

This training can be effected without making boys embryo 
chemists, or electrical engineers, or biologists; without follow- 
ing courses of work based on syllabuses of the type of those 
for university entrance examinations, syllabuses designed to 
serve as preliminary studies of a professional type, to be 
extended later. Such courses are too specialized and too 
limited. It is true that a small amount of very exact quantitative 
work may be done by a boy working for his school certificate, 
but at what a cost! He may be able to find the specific heat 
of a metal accurately to three places of decimals, to find the 
refractive index of a prism, to obtain wonderfully correct 
results in troublesome gravimetric and volumetric analyses; 
and yet he will probably have no idea how the distance of the 
sun was discovered, how a plant breathes, how animals are 
classified, or that his own body is the most perfect combustion 
engine in the world; and he will be just as ignorant of scores 
of other things about which every intelligent person ought to 
have a clear understanding. He probably does not know a 
tithe of the scientific words in common use, and more likely 
than not he is ignorant of the nature of many everyday 



THE PURPOSE OF SCIENCE TEACHING 13 

phenomena and of the applications of many common scientific 
principles. The literature of scientific subjects is probably 
almost as unintelligible to him as to boys who have never 
been taught science at all. 



Formal Training versus Cultural Value 

All down through the ages educators have quarrelled over 
this question: should the chief aim of education be formative 
or informational? mind-training or mind-filling? In the 
teaching of science there can be no doubt about the reply: 
both are equally necessary. Neither must be sacrificed to the 
other, neither given priority. Forty years ago, intellectual 
training had given place to the doling out of knowledge; then 
the pendulum swung violently back, and intellectual training 
was given an advocacy that soon made it paramount. Now 
the pendulum is swinging again in the opposite direction. 
The partisanship cannot be justified, and it is for science 
teachers to see that a proper balance is preserved. 

Here is a suggestive extract from a recent letter to Nature. 
" While science has now illuminated the Western world for 
some hundred years, no bold attempt has yet been made to 
reorganize and direct our social system in keeping with it. 
It has been given no cultural value, although it has had a 
profound and disturbing effect on all previous types of culture 
and aesthetic ideals. The coming of science and industry 
has completely changed the world. It has given us social, 
economic, and international problems which cry aloud for 
scientific solutions, but unless the mass of people is trained 
in the atmosphere of science, it will persist in attempting to 
solve these problems on traditional mediaeval lines." This is 
an .accurate reflection of the opinion of many thoughtful men, 
and every science teacher should see to it that he does his 
share towards solving the very difficult problem of giving 
science an adequate cultural value as well as making it a subject 
for training the mind. 



14 SCIENCE TEACHING 

CHAPTER III 

Methods 

Methods of By -gone Ages 

Are our methods of teaching superior to the methods of 
such teachers of by-gone ages as Plato and Aristotle? 

Plato and his pupil Aristotle are the great exemplars of 
the two contrasted teaching methods that have always divided 
schoolmasters into two camps. Plato's method was to dig into 
his own mind for first principles, submit these to the most 
drastic criticism, and then to build up a system upon them 
as foundations. His method was wholly deductive. His famous 
pupil Aristotle broke away from this method and called for 
facts. Aristotle's method was essentially inductive. His founda- 
tions were facts about which people were in general agreement. 
He profoundly distrusted Plato's apriorism, yet, curiously 
enough, he often violated his own rules. 

Plato's main interest was in man, rather than in nature 
in the wider sense. Aristotle's interests were more compre- 
hensive. True, Aristotle was as keen a student of man as Plato 
was, but he took the whole of nature for his province. In 
criticizing Aristotle, we must bear in mind that in his time 
experimentation was in its infancy. Such experiments as 
were attempted were necessarily crude. Of apparatus there 
was really none, and of methods of scientific investigation 
there were no established principles at all. 

Some 2000 years later, another great exponent of the 
inductive method arose, an Englishman, Francis Bacon. He 
laid it down as a fundamentally necessary thing that progress 
in knowledge depended on the accumulation of facts, a sifting 
of the facts, an organization of the facts, and a search for 
similarities and differences. Aristotle and Bacon were the two 
first great advocates of the method which it behoves all students 
and teachers of science to follow. It is true that Baffon, like 



METHODS 15 

Aristotle, often broke his own rules, but it is hardly surprising 
that tye was occasionally enmeshed in the traditional systems of 
medievalism. 

But Plato's method also plays a part in science teaching, 
a more important part than is commonly admitted. It was 
Plato's custom to ask his pupils these questions: State what 
you really know about this thing; give an exact explanation 
of every term you use in your description; how do you know 
that your statements are true? on what principles is your 
reasoning based? how did you ascertain the truth of those 
principles? how did you reason out your conclusion? Surely 
this is a model form of questionnaire for every science teacher, 
to apply both to himself and to his pupils. 

Plato was a ruthless critic of other people's conclusions. 
He would almost always catch his disciples tripping some- 
where. Even his most brilliant students would sometimes use 
a word in slightly different senses, and that difference would 
inevitably lead to a student's discomfiture. Aristotle set to 
work in an entirely different way. He called for observation 
and experiment, for facts, and still more facts; now organize 
your facts, he said; what inference can you draw from that array 
of facts? are you quite certain that the inference is justified? 

So it was with Bacon. 

Science teachers may learn much from both Aristotle and 
Plato; so may science examiners. 

Science Teaching from 1867 

Down to the middle of the nineteenth century, science was 
the veritable Cinderella of the British school curriculum. 
Science itself was making headway, but science teachers were 
few, and those few were engaged in fighting down opposition 
all round. Canon Wilson,* afterwards Headmaster of Clifton, 
was the recognized protagonist, and in 1867 he rang up the 
curtain on modern science teaching. We may quote from his 
book: 

* Canon Wilson is still with us, apparently as intellectually alert' as ever. 



16 SCIENCE TEACHING 

" Science is the best teacher of accurate, acute, and exhaustive 
observation of what is; it encourages the habit of mind ^vhich 
will rest on nothing but what is true; truth is the ultimate 
and only object, and there is the ever-recurring appeal to facts 
as the test of truth. " 

" Science teaches what evidence is, what proof is." 

" It is important to distinguish between scientific information 
and training in science. Both of these are valuable, but the 
scientific habit of mind, which is the principal benefit resulting 
from scientific training, can better be attained by a thorough 
knowledge of the facts and principles of one science than by 
a general acquaintance with many." 

" The lecture may be very clear and good; and this will 
be an attractive and not difficult method of teaching, and will 
meet most of the requirements. It fails, however, in one. 
The boy is helped over all the difficulties; he is never brought 
face to face with nature and her problems; what cost the 
world centuries of thought is told him in a minute; his atten- 
tion, understanding, and memory are all exercised; but the 
one power which the study of physical science ought pre- 
eminently to exercise, the power of bringing the mind into 
contact with facts, of seizing their relations, of eliminating the 
irrelevant by experiment and comparison, of groping after 
ideas and testing them by their adequacy in a word, of 
exercising all the active faculties which are required for an 
investigation in any matter these may lie dormant in the 
class while the most learned lecturer experiments with facility 
and explains with clearness." 

" A master who is teaching a class quite unfamiliar with 
scientific method, ought to make his class teach themselves , 
by thinking out the subject of the lecture with them, taking 
up their suggestions and illustrations and criticizing thetn> 
hunting them down, and proving a suggestion barren or an 
illustration inept." 

All this r^ads as if written in 1928 instead of more than 
sixty years ago. Canon Wilson's advocacy soon began to bear 



METHODS 17 

fruit. Some progress in providing facilities for practical work 
was made even in the seventies; in the eighties, laboratories 
of sorts began to multiply; but until the early nineties 
progress in this direction was slow. 

Every now and then a new educational prophet arises. 
He tells us that everything is wrong, and that he alone possesses 
the key for putting everything right. Those of us who have 
watched the rise and fall of many prophets are driven to the 
conclusion that real progress in methods is a thing of exceedingly 
slow growth, and that it is stupidly false to assert that present- 
day methods are conspicuously more successful than the 
methods of a generation or two ago. And, after all, it is not 
so much the method that counts as the man. 

Nevertheless, the methods of science teaching have un- 
doubtedly improved in some measure. 

The Methods of Forty Years Ago 

Forty years ago, there were few school laboratories avail- 
able, and these were usually poorly equipped, and such science 
teaching as was done was usually done at the demonstration 
table; but even for this work the equipment provided was 
generally meagre in the extreme. 

In those days, as now, a certain number of science teachers 
gave " lectures " to their classes, sometimes using their own 
lecture-notes of college days. And in those days, as now, 
such lectures were wholly ineffective. " Lectures " to univer- 
sity students are, of course, the normal thing, and lectures 
to a Sixth Form are often quite appropriate: students of 
trained intelligence want something to bite at. But lectures 
to younger boys are out of place, a principle which was as 
fitlly recognized by the majority of teachers forty years ago 
as by teachers of the present day. Most teachers of that time 
really taught; they did not merely talk; and more often than 
not the boys were remarkably keen on their science lessons. 
At each step of the demonstration, they had ^to describe in 
accurate language what had been done, and they \vere there- 



x8 SCIENCE TEACHING 

fore compelled to observe carefully; then they had to say 
what might be inferred, and the discussions concerning the 
false inferences which pupils often drew were not infrequently 
of great value. Lastly, the results of a series of experiments 
were sometimes happily collated, and some point of theory 
worked out. Many of the pioneers of those days were really 
clever teachers and fully deserved the reputations they 
enjoyed. 

Of course there were exceptions. I had my own first lesson 
in chemistry at the age of ten. We had no laboratory of any 
kind, but we did have a well-equipped demonstration table, 
and a plentiful supply of reagents, and the subject was taken by 
the visiting borough analyst. The first lesson of all how well 
I remember it was (of course!) on hydrogen, and lasted an 
hour. After spending a quarter of an hour on the preparation 
of the gas and a demonstration of its properties, the lecturer 
developed the atomic theory, and it is quite certain that he 
would have included large doses of isotopes and electrons if 
he had ever heard of them. Naturally the whole thing was a 
failure. But, then, teaching was not his professional work. 
For aught I know he would have added still further to his 
income by taking on, with the same royal confidence, an 
operation in surgery. 

Such practical work as was done by pupils themselves in 
those days was almost always confined to chemistry, and to 
one small corner of that, namely, qualitative analysis, " test- 
tubing ", as some unkind critic has called it. Certainly the 
work was often unintelligently done. The teacher provided 
analytical tables, and a laboratory boy kept a Kipp in going 
order and the working-bench shelves stocked with the usual 
two dozen bottles of ordinary reagents, in addition to the few 
special reagents less frequently wanted. Nearly everything eke 
was left to the pupils' own inner light, and they soon got 
into the habit of just saying, " Yellow: that's cadmium "; and 
so on. 

But sometimes the work was so well done as to be of very 
substantial^ value. A preliminary discussion on solubilities 



METHODS 19 

would lead to a boy's discovering for himself how to detect 
and then how to separate silver and mercury in a mixture of 
salts of those metals, then how to separate any two members 
of the first group, then how to construct a complete separation 
table for that group. By that time a boy began to realize the 
inner significance of the separation tables, and the work there- 
after proceeded intelligently. 

The same work was sometimes happily associated with the 
systematic study of the common metals, at the demonstration 
table, often with valuable results. And sometimes it was 
associated with the elementary study of pigments, an interest- 
ing development too often overlooked nowadays. Still, it must 
be admitted that qualitative analysis was given too prominent 
a place; it became too elaborated, and much practice made it 
wholly mechanical; tricky mixtures were given in examinations 
that demanded an entirely disproportionate amount of time for 
previous laboratory practice, and all other forms of practical 
work were neglected. Physics received little or no attention, 
and thus much of the experimental work in chemistry was 
not understood. But qualitative analysis may be made a valu- 
able adjunct to any course in chemistry. 

When I began teaching in 1886, I was given the oppor- 
tunity, rather reluctantly, to give two lessons a week in chemis- 
try, as well as the regulation two lessons in mechanics. There 
was no laboratory and no fitted demonstration table. The 
only balance available was a home-made one costing about 
35. 6</., with scraps of metal for the smaller weights. It weighed 
fairly accurately to one decimal place. The apparatus in stock 
was worth perhaps 2, and we were quite proud of our bunsen 
burner attached by rubber tubing to the gas pendant above 
our heads. I had discovered a book by an American professor, 
IraRemsen, a revelation as to method in those days. In the 
middle of a lesson on equivalents, two visitors whose names 
I did not catch were shown in, and they sat down and listened. 
When I had finished they came up and showed what I thought 
to be a surprising appreciation of what I had beqjn doing, and 
eventually one of them said: " Do you happen* to know 



20 SCIENCE TEACHING 

Roscoe's book on chemistry?" " Yes," I replied, " and a 
thoroughly unsatisfactory book it is. The writer makes un- 
justifiable assumptions about chemical theory before ne has 
established necessary facts. It is the kind of thing that no 
teacher ought to do." At this stage the second visitor inter- 
posed and said, " I think, perhaps, you are asking for trouble. 
Let me introduce you to Professor [afterwards Sir Henry] 
Roscoe." However, in spite of the criticized book, I learnt 
more about the teaching of chemistry in the next quarter of 
an hour than I might have learnt in the next ten years. In 
particular I learnt a much needed lesson that there is more 
than one avenue of approach to the teaching of science, and 
that it is sheer folly to assume that science must be taught 
according to some particular pedagogue's prescription. 

The advance in the forty years has not been in the direction 
of more telling work at the demonstration table, but in the 
direction of systematized laboratory training. 

The " Heuristic " Method 

Perhaps the most impatient man in the world of science 
teaching during the late eighties and the nineties was Dr. 
H. E. Armstrong, Professor of Chemistry at the City and 
Guilds Institute, South Kensington, still (1928) capable of 
hitting out as straight and hard as in 1888. Apparently the 
adolescent boys who were sent to him to learn chemistry 
were badly grounded in elementary science, and had little 
knowledge of any sort of methodical procedure; and he com- 
plained bitterly of the ineffective teaching in the schools whence 
they came. Thenceforward he became a strong advocate of a 
special type of laboratory training, and he revived the rather 
unfortunate term " heuristic " (etynWo = I discover), tind 
thereby gave the philistines their opportunity. Had the word 
adopted suggested search instead of discovery, the philistines 
would have been disarmed. 

Many yesys ago I asked a young science master, who talked 
a great ieal about methods, if I might invite his classical 



METHODS 21 

headmaster to be present at a first lesson on electricity. He 
assented readily, and the lesson was given. He had the usual 
stock (in those days) of glass rods, sticks of sealing-wax, 
ebonite, silk, flannel, and pith-ball and gold-leaf electroscopes, 
worked the usual experiments, and tabulated in two columns 
on the blackboard his differentiated results. So far, excellent. 
Then he began to get the boys to draw inferences, first telling 
them that they must not talk of two kinds of electricity but 
of two kinds of electrification. The boys* general conclusion, 
arrived at as a result of a string of leading questions from the 
teacher, questions which almost put into the boys' mouths 
the words the teacher wanted, were that like electrifications 
repel, unlike electrifications attract. The boys were then told 
that this was a " law ", and that they had " discovered " it. 
Naturally the headmaster, a particularly clear-headed man, 
pounced at once upon " such shoddy reasoning ". " All that 
you have done is to sort out the things you rubbed and the 
things you rubbed with into two classes (though even this dis- 
tinction is not logically justified, for you rubbed the silk with 
the glass rod just as much as you rubbed the glass rod with the 
silk), and you sorted out the results according to the move- 
ments of the pith-ball; it was obvious that you were making 
use of previous knowledge, for you took care always to rub the 
glass rod with silk, and the sealing-wax with flannel. How 
then are you justified in saying that you have ' discovered ' that 
all substances are divisible into two groups producing opposite 
effects? And how can you say that there are two kinds of 
electrification? Why two kinds of electrification rather than 
two kinds of moonshine? Your classification of the experi- 
mental facts is not logical and your conclusions not justified, 
I know nothing of the subject but what I have learnt from 
yoilr lesson, but it is obvious to me that your conclusion is 
not an inference at all, but an hypothesis, in other words a 
guess, put forward to ' explain ' your particular grouping of 
facts. And why did you use the words attract and repel to 
describe the movement of the pith-ball? You might have said 
that the pith-ball moved as if there were attraction and 



22 SCIENCE TEACHING 

repulsion, but there was no evidence whatever in your experi- 
ments to explain why the ball moved as it did. Surely^at this 
stage you should have been content to describe, and not put 
forward an hypothesis which you cannot support. If this is 
what you call science teaching I prefer that the boys devote 
their time to some other subject. " 

The headmaster's pungent criticism was fully justified. 
The grouping of facts is a relatively simple matter. The 
41 discovery " of the logical conclusion that may be drawn 
from such grouping is more often than not something entirely 
beyond the skill of the beginner. 

There is thus a need to use the word " discovery " 
cautiously. 

Professor Armstrong describes the (so-called) heuristic 
method thus: 

" Heuristic methods of teaching are methods which involve 
our placing students as far as possible in the attitude of the 
discoverer methods which involve their finding out instead 
of being merely told about things/' 

" The student is required to solve a number of problems 
experimentally: to determine, for example, the composition 
of air and water; and the idea of measurement is introduced 
from the very beginning, as the determination is made quan- 
titatively as well as qualitatively. Each student receives a 
paper of instructions which are advisedly made as bare as 
possible so as to lead him to find out for himself or inquire 
how to set to work; he is particularly directed that, having 
made an experiment, he is to enter in his note-book an account 
of what he has done and of the result; and he is then and 
there to ask himself what bearing the result has upon the parti- 
cular problem under consideration: having done so, he is. to 
write down his conclusion. He is thus at once led to consider 
what each experiment teaches: in other words, to reason from 
observation. " 

All this is admirable advice. We now give one of his " papers 
of instructions ": 



METHODS 23 

" PROBLEM: To DETERMINE THE COMPOSITION OF AIR 

" N.B. Be especially on your guard against drawing con- 
clusions which are not justified by the result of the experiment; 
but, on the other hand, endeavour to extract as much infor- 
mation as possible from the experiment. 

" i. Burn a piece of dry phosphorus in a confined volume 
of air, i.e. in a stout Florence flask closed by a caoutchouc 
stopper. Afterwards withdraw the stopper under water, again 
insert it when water ceases to enter, and measure the amount 
of water sucked in. Afterwards determine the capacity of the 
flask by filling it with water and measuring this water. 

" N.B. The first part of this experiment requires care and 
must be done under direction. 

"2. Allow a stick of phosphorus lashed to a piece of stout 
wire to remain for some hours in contact with a known volume 
of air confined over water in a graduated cylinder. After 
noting the volume of the residual gas, introduce a burning 
taper or wooden splinter into it. 

" N.B. The residual gas is called nitrogen. 

" 3. Burn a piece of dry phosphorus in a current of air 
in a tube closely packed with asbestos. Weigh the tube, &c., 
before and after the experiment. 

" 4. Repeat experiment 2 with iron borings moistened with 
ammonium chloride solution. Preserve the residual gas. 

" 5. Suspend a magnet from one arm of a balance; having 
dipped it into finely divided iron, place weights in the opposite 
pan; when the balance is in equilibrium, set fire to the iron. 

" 6. Pass a current of dry air through a moderately heated 
tube containing copper. Weigh the tube before and after the 
experiment; note also the alteration in the appearance of the 
copper. 

" 7. Strongly heat in a dry test-tube the red substance 
obtained by heating mercury in contact with air. At intervals 

* This is apparently the first problem of Professor Armstrong's chemistry 
course. " The second problem of the course: to determine the composition of 
water " (pp. 227-8). " Having studied air, water ", &c. (p. 2,^o^Method of Teach- 
ing Chemistry). 



24 SCIENCE TEACHING 

plunge a glowing splinter into the tube. Afterwards note the 
appearance of the sides of the tube. (Before performing this 
experiment, ask for directions.) 

" N.B. The gas obtained in this experiment is named 
oxygen. 

" 8. Heat a mixture of manganese dioxide and potassium 
chlorate in a dry test-tube; at intervals plunge a glowing 
splinter into the tube. This experiment is to acquaint you with 
an easy method of preparing oxygen in quantity. 

"9. Prepare oxygen as in experiment 8 and add it to the 
nitrogen from experiment 4 in sufficient quantity to make up 
the bulk to that of the air taken for the latter experiment. 
Test the mixture with a burning taper or splinter. 

" 10. Dissolve copper in nitric acid and collect the escaping 
gas (nitric oxide); add some of it to oxygen and some of it to air. 

" ii. Fill a large flask provided with a well-fitting caoutchouc 
stopper and delivery tube with ordinary tap water and gradually 
heat the water to the boiling-point; collect the gas which is 
given off in a small cylinder and add nitric oxide to it. Also 
collect a sufficient quantity in a narrow graduated cylinder 
and treat it as in experiment 2." 

Twenty-five years ago I saw this paper of instructions in 
use on several occasions. Never were the results quite satis- 
factory. For beginners the instructions are inadequate. Indeed, 
this is admitted: " the first part of the experiment must be 
done under direction "; " before performing this experiment, 
ask for directions ". A dozen boys besieging a teacher with 
questions, while another dozen are busy making all sorts of 
experimental blunders, perhaps trying to lash a stick of phos- 
phorus to a piece of wire, perhaps trying to " obtain " " the 
red substance " by heating mercury in contact with air, is a 
sight to see. Even with a small number of boys, the whole 
investigation takes half a term, with the time ordinarily avail- 
able. Let it be assumed that the training in method may be 
an unqualified success; from the point of view of knowledge 
gained, the half-term's work is wholly inadequate. One general 



METHODS 25 

complaint made by teachers in those days was that difficulties 
constantly arose because the chemistry course was not pre- 
ceded by a course of elementary physics. The phrase " sucked 
in " in experiment i suggests that no such course was intended 
and that this seriously incorrect explanation of a physical 
happening may be accepted. 

Apart, however, from details possibly open to criticism, is 
the general principle of the method sound? Merely from the 
point of view of training in method, the plan, in the hands of 
the exceptional teacher, works well with a very small number 
of boys, say four or five, where the teacher can be at the elbow 
of each throughout the lesson. But how much does the pupil 
really discover for himself? Who does the real thinking, teacher 
or pupil? Of course with such a small number of pupils a 
teacher would at each step tell each inquirer just enough, but 
no more, to enable him to proceed. But when a dozen pupils 
are all clamouring for help at the same time, how can answers 
to inquiries be well thought out? In fact the method presupposes 
a very small class and a gifted teacher. 

On one occasion in those days, a brilliant young master, 
now one of our most distinguished chemists, who had been 
brought up in the heuristic school, gave his first lesson in my 
presence. His chief had said to me: " I have just appointed 
a man who really does believe he can majie the heuristic method 
a success/' For his first lesson he had hoped to have a class of 
about half a dozen boys, but to his amazement he found that 
he had to take forty. He made " the composition of water " 
the subject of his lesson, and he began by preparing in a variety 
of ways supplies of hydrogen and oxygen. Experimentally the 
lecture (it did not pretend to be anything else) was a tremen- 
dous success flashes, flames, sparks, and explosions galore. 
Neyer w r ere boys more interested. At the end I asked them what 
the lesson had been about, and one little urchin said: " Fire- 
works, sir." When I gently chided the master for surrendering 
his principles, he replied: " But I was scared out of my life 
at the prospect of facing that crowd of boys." He had rightly 
divined that discipline must be given prioritv over method. 



26 SCIENCE TEACHING 

^Essentially, the heuristic method is intended to provide a 
training in method. Knowledge is a secondary consideration 
altogether. The method is formative rather than informational. 
Such training, if properly carried out, does cultivate painstaking 
and observant habits, and encourages intelligent and indepen- 
dent reasoning. It does bring home to boys clear notions of 
the nature of experimental evidence, and the boys do learn 
that answers to questions can often be obtained from experi- 
ments they can work for themselves. 

On the other hand, progress is inordinately slow, even with 
exceptional teachers. Far too little ground is covered in a 
term. The work attempted is confined almost entirely to 
physics * and chemistry, and boys get a wrong idea of science 
as a whole, or, for that matter, of physics and chemistry as a 
whole. The succession of exercises is rarely planned to fit 
into a general scheme for building up a subject completely; 
bits of a subject are chosen just because they lend themselves 
best to the particular type of training. Time is wasted over 
experiments that are beyond the pupils' skill and ought to be 
performed by the teacher. The whole method tends to be 
spoilt by its background of false perspective. 

Unless the term " discovery " is confined to just the final 
result that naturally follows from suggestions and leading 
questions made by the teacher, it had better not be used. A 
boy never " discovers " a principle, and it is doing him a 
disservice to let him think he does. Above all things, science 
teaching demands intellectual honesty. 

At the same time, no system of science teaching is likely 
to be effective unless it is animated by a spirit of search, whether 
at the demonstration table or in the laboratory. The pupil 
ought to see that the work he is engaged in, or that his teacher 
is engaged in, is a problem, and a problem worth solving, not 
merely a laboratory " exercise ". The teacher should keep 
the pupil's mind in a state of tension; he should compel the 
pupil to follow up the details of an experiment, and to piece 

* Physics as y^ell as chemistry have been included in all school courses for 
many 



METHODS 27 

the details together; but the pupil's own inference, if correct, 
will n^ver contain more than was included in the experiment, 
save something drawn from his stock of old knowledge. If 
the conclusion contains something previously unknown, that 
something was in all probability provided, somehow and some- 
when, by the teacher. A beginner in science may " discover " 
a test-tube hidden in a drawer, but he will rarely or never 
discover a principle lurking in a group of facts. The boy may 
be taught to experiment, to observe, to sort out, to record, 
and to do all those things unaided; and he may be taught to 
search for resemblances and differences; but the new thing, 
the unknown thing, has, as a rule, to be given him. 

The attempt to teach science merely for the sake of the 
training it may afford has resulted in much ineffective work. 
Still, " the spirit of inquiry " should most certainly be en- 
couraged, and should run through any course of science teach- 
ing. By all means get boys interested in common occurrences, 
and lead them to follow up clues as to possible causes. Boys 
love to solve puzzles, to unravel mysteries. Encourage them to 
devise experiments to test their own explanations of things they 
have observed. Make them keen inquirers. Encourage habits 
of independent thinking about evidence obtained first hand/j 

* I have never had the privilege of hearing Professor Armstrong teach, but I 
have learnt from several of his old pupils a good deal about his methods, and I am 
driven to the conclusion that he has never told us in either his books or his lectures 
what the secret of his method is. And I doubt if he is really aware of his own secret, 
any more than Colburn the calculator was, or any other person with exceptional gifts. 
His secret is not to be found in the use of the balance, or in heuristics, but probably 
in his own personality his rather tart impatience towards his students, his refusal 
to help them one iota more than is absolutely necessary, his amazingly clever and 
ever-ready questions to meet the needs of the moment, his resourcefulness under 
all experimental difficulties, his untiring help to his students, his rather " grumpy 
manner ", and his rare words of praise. Said one old student, " We didn't like him 
at all at first, but he was a clever teacher. We felt he could almost see the thoughts in 
our minds and tell exactly how much help we really wanted in order to overcome 
our difficulties. Of course we never discovered anything important ourselves. We 
got that from Professor Armstrong or from books. But I think most of us did 
learn to understand things pretty clearly." 

I wonder if Professor Armstrong, during all his teaching experience, ever had 
to teach a class of really dull students? Doubtless he has had new students totally 
ignorant of science, perhaps clumsy and stupid when first turned on to experi- 
mental work. But a class of really unintelligent students? I doubt it. Certainly 
not if those of his old students with whom I am acquainted are any criterion. 
He would hardly call a beginner unintelligent for failing to obtain the "red sub- 
stance" from mercury heated in contact with air! 

(K72) 



28 SCIENCE TEACHING 

Lecture -room and Laboratory 

The heuristic method is supposed to be based exclusively 
on laboratory work, the lecture-room being abolished. Its 
exponents sometimes grudgingly make the concession that 
formal lessons at the demonstration table are occdsionally 
required to supplant the laboratory work, to drive home facts, 
and to clarify things generally. In actual practice, all teachers 
give such lessons, knowing well that otherwise their pupils' 
knowledge will remain nebulous, and their ideas more nebulous 
still. 

Suppose that the work at the demonstration table takes the 
place altogether of work in the laboratory. Suppose that the 
teacher does all the experimental work and the pupil does none. 
What then? 

First of all, what is a " lecture-room "? The term is 
appropriate enough in a college; perhaps even in a school, for 
the Sixth Form. But for younger pupils lectures qua lectures 
are out of place. Such pupils cannot follow chains of reasoning. 
They must be given one point, or at most a few points, at a 
time, and these must be understood and known before farther 
points are considered. The veriest tyro of a teacher knows this. 
But what is a " demonstration table " and what is a demon- 
strator? Properly speaking, a demonstrator is one who performs 
experiments to illustrate, to confirm, to verify facts and prin- 
ciples enunciated by the lecturer. The assembled students 
listen, observe, and make notes. Formally they are not 
" taught ". They are not examined or cross-examined. If 
they do not digest the fare provided, that is their look-out. 

But in a school the lecture-room is a place for teaching, 
and the demonstration table is the teacher's laboratory bench. 
The teacher works experiments, often because the experiments 
are beyond the pupils' skill; the lesson consists of questions 
and answers all the time directed questions, and in case of 
emergency leading questions, and answers which are used for 
cross-examination and for further questions. The teacher does 
not wock experiments primarily to verify, but to present new 



METHODS 29 

facts; and such facts thus presented at first hand are made 
the bas^ of the whole lesson. It is true that the pupils are not 
using their hands, but it is this freedom that enables them to 
give all their attention to the teacher; their attention is not 
divided by their having to engage in difficulties of manipulation. 
(It is, of course, assumed that the teacher is able to compel 
sustained attention.) 

Who shall say that such a method may not be effective? 

Suppose that a teacher plans out a course of work in a 
subject, then makes out a list of all the experiments he con- 
siders necessary for establishing facts and principles, ticks off 
those experiments which can safely be left for the pupils to 
do, and decides to reserve the rest to be done by himself at 
the demonstration table. Who shall criticize him for such a 
division of labour? 

The success of present-day science teaching in this country 
and much of it is undoubtedly successful is probably largely 
due to a happy combination of demonstration-table and labora- 
tory training. The Germans are not great believers in laboratory 
training for pupils (at all events were not, in pre-war days); 
they argue that it is wise policy not to give the pupils an oppor- 
tunity of making mistakes. The Americans, on the other hand, 
tend to pin their faith to laboratory methods, methods which 
are, however, more strictly inductive than they are " heuristic ". 
Americans, including Canadians, have devoted an enormous 
amount of attention to methods of teaching, and it is doubtful 
if they have very much to learn from us. Their prepared 
" instructions " for pupils* laboratory work are often remark- 
ably good. 

The Germans ascribe much of their national thoroughness 
to their system of science teaching by lectures. The Americans 
ascnbe much of their national keenness to their system of 
laboratory training, essentially a training on inductive and 
problem-solving lines. 



30 SCIENCE TEACHING 

Lecture -room versus Laboratory 

Attempts have been made in America to estimate the 
relative values of work done by the " lecture " method and 
the laboratory method. One plan consisted in preparing a 
course of work for two classes of pupils, the course being given 
to one class in the lecture-room, the pupils of this class doing 
no experimental work at all, and to the other class in the 
laboratory, the teacher in this case doing no experimental work 
at all but giving such individual help as might be wanted from 
time to time. The two classes were of about the same average 
age, and of about the same average ability. For the laboratory 
class, very detailed papers of instructions were prepared, and 
a copy given to each pupil in order that he might set to work 
with a minimum of help from the teacher. A copy of the 
same instructions was given to, and had to be followed out 
by, the teacher in the lecture-room. At the end of the course, 
an examination was held, the same for both classes. The 
result was in favour of the lecture; the pupils had clearer 
ideas of what they had been taught, and they remembered 
their facts better. Three months later, a second examination 
was held, the questions being different from those at the first 
examination. Neither the teachers nor the pupils had been 
warned of this second examination, so that there was no sort 
of special revision. This time the result was slightly in favour 
of the laboratory pupils, who remembered the details of the 
experiments better than did their competitors; the latter, 
however, still had rather clearer ideas of what the aims of the 
experiments had been. But the most interesting fact is this: 
that the next term the " lecture " pupils not only attacked new 
problems better than the " laboratory " pupils, but were 
actually more skilful in laboratory manipulation. 

It is quite unsafe to draw any general inference from such 
an experiment. The data are too scanty, the factors involved 
too variable. The experiment might with advantage be repeated, 
other expei? ments with the same end in view be devised, and 
the resales of the different experiments compared. It is evident, 



METHODS 31 

however, that those who roundly condemn lessons given in the 
lecture-room should pause. If it can be shown that the lecture- 
room n!ethod is as good as the laboratory method, both as to 
training and as to knowledge imparted, a great saving of time 
might be effected in our science teaching. 
But we must suspend judgment. 

The Historical Method 

Some science teachers are strong advocates of developing 
a subject, not by first establishing accepted principles but by 
following the order in which investigators all down through 
the ages have gradually worked out the subject from its early 
beginnings. It is urged that chemistry in particular lends 
itself well to this treatment, that it is highly instructive to let 
a boy see how one hypothesis after another has been over- 
thrown in the light of new facts, and that only in this way 
does he ever learn to adjudicate the real worth of scientific 
theory. It is, of course, an excellent thing for a boy to form 
the habit of asking whether an hypothesis is adequately sup- 
ported by facts, and thus to learn that he must never try to 
make his facts fit the hypothesis. And no doubt the gradual 
development of the atomic theory can be unfolded historically 
in a very illuminating way. 

The method can be pursued either in the laboratory or in 
the lecture-room or in both. But it is by no means always 
easy, indeed not always possible, to repeat the experiments of 
early investigators. A more serious objection is the inevitably 
slow progress which results from the method. It simply does 
not pay to spend a whole lesson over, say, the phlogiston hypo- 
thesis. Moreover, fundamental principles are apt to be obscured 
both by experimental details and by incidents in the lives of 
former investigators, details and incidents that are not worth 
remembering. 

But some subjects, especially those that do not lend them- 
selves to experimental treatment, may be developed historically, 
and to great advantage. In what better way can astronomy be 



32 SCIENCE TEACHING 

taught to an upper form than by successively taking up the 
work of Ptolemy, Copernicus, Kepler, Galileo, Newton, Kirch- 
hoff, and others? And if only a very limited amount* of time 
can be devoted to geology, what better general outline can be 
found for a Sixth Form than in Geikie's Geologists? Then there 
is much to be said for developing the subject of mechanics 
historically. Two lessons a week for a term could be pro- 
fitably spent over the work of Stevinus, Pascal, Kepler, and 
Newton; and in this way, as in no other, the foundations 
of mechanics are likely to be well and truly laid, especially if 
Mach's criticisms are taken to heart. 

Well-known stories from the history of science, such as 
Archimedes and his bath, Newton's question why the moon 
does not fall as an apple falls, always appeal strongly to a boy, 
and may be made the means of arousing interest for wrestling 
with the difficulty of a new principle. And such a book as Sir 
Richard Gregory's Discovery ought to be read by every Sixth 
Form boy in every school, whether science is his special subject 
or not. It is full of good stuff, stuff with which every educated 
person ought to be familiar. 

If the historical method is adopted, the general method of 
the history teacher must be followed. The boy must be taken 
back and immersed in the period under study, be made not 
only to live with the people of that time and in their environ- 
ment, but also to understand the stage and state of knowledge 
of the time and what materials the investigator then had to 
work upon. What is the use of discussing Roger Bacon and his 
work unless a boy first understands something of the spirit 
of medievalism that any person who attempted to unravel 
nature's secrets must be a special emissary of Satan himsejf, 
and be punished accordingly. 

On balance, it may be said that teaching in accordance 
with historical sequence is not to be recommended for subjects 
usually taught up to the Fifth Form physics, chemistry, and 
biology. 

The teaching of the history of science generally is quite 
another palter, and provision should always be made for it. 



METHODS 33 

Huxley's Method 

So* far as I know, Huxley never taught in a school, but 
those of us who sat under him as a lecturer never hesitated to 
say that he was the most brilliant teacher we had ever known. 
His lucidity of exposition was extraordinary. As far back as 
1869 he gave a course of lectures to young people at the Royal 
Institution, his subject being physiography. The lectures were 
afterwards printed in book form, and for more than a generation 
the book was regarded as a model of scientific method. 

But this was before the days of school laboratories. The 
lectures were frankly lectures, illustrated by experiments. 
Huxley said: " It appeared to me to be plainly dictated by 
common sense that the teacher who wishes to lead his pupils 
to form a clear mental picture of the order which pervades 
the multiform and endlessly shifting phenomena of nature, 
should commence with the familiar facts of the scholar's daily 
experience; and that, from the firm ground of such experience, 
he should lead the beginner, step by step, to remoter objects 
and to the less readily comprehensible relations of things. I 
conceived that a vast amount of knowledge respecting natural 
phenomena and their interdependence, and even some practical 
experience of scientific method, could be conveyed, with all 
the precision of statement, which is what distinguishes science 
from common information. And I thought that my plan would 
not only yield results of value in themselves, but would facilitate 
the subsequent entrance of the learners into the portals of the 
special science/' 

Huxley began w r ith the familiar phenomena of a local river 
basin, and showed that the muddy waters of the river, the hills 
between which it flows, the breezes which blew over it, are not 
isolated phenomena to be taken as understood because familiar; 
but that the application of the plainest and simplest processes 
of reasoning to any one of these phenomena suffices to show, 
lying behind it, a cause, which again suggests another; until, 
step by step, the conviction dawns upon the learner that, to 
attain even an elementary conception of what gcfe* on in his 



34 SCIENCE TEACHING 

parish, he must know something about the universe. Thus 
Huxley worked out, in a most admirable way, the principles 
of what we should now call physical geography, all traceable 
to the elementary principles of physics, chemistry, biology, 
and elementary astronomy. Huxley's pupils were active and 
not merely passive listeners; they learnt. They could not but 
learn, for Huxley was a born teacher, and the machinery of his 
method counted for little. His method embodied, in its spirit 
and mode of presentation, the true principles of scientific 
method. His scheme was an ever ramifying logical develop- 
ment from facts already familiar to the learner. 

The * 4 Concentric " Method 

This is less a method than a scheme of organization. It is 
exemplified in the late Professor Sylvanus Thompson's book 
on magnetism and electricity, in which the whole ground is 
covered twice, the first time in outline, simply and qualitatively; 
the second in greater detail, with elementary mathematical 
considerations and with some approach to general complete- 
ness. The principle is, of course, that, in school practice, a 
subject can seldom be begun and be given an exhaustive 
treatment as it proceeds. A first and sin pie presentation of a 
subject may, often with advantage, be given to boys of, say, 
14, gaps filled in the following year, and perhaps further gaps 
a year or two later still. This applies particularly to the different 
branches of physics. In the case of chemistry, the subject may 
be so organized that going back to early work, except for 
revision purposes, is less necessary. It is all a question of 
what pupils are capable of assimilating at each stage of their 
course. 

We give two illustrations of this grading principle. Sup- 
pose that the subject to be taught is the rainbow. The whole of 
the necessary work might be divided into three distinct stages: 

Stage I. Boys 12 to 14. Work wholly observational. (The 
phenomenon being comparatively rare, there would be no 
objection to*a particular class being given the first opportunity 



METHODS 35 

that occurred for making actual observations outside the school.) 
From a whole class, under guidance, the following observations 
might 7>e expected, written records afterwards being made: 
{a) the obvious conditions of occurrence the rays of the sun 
shining on falling drops of rain; (/;) the brilliant colours of 
the bow, and their order; (c) the reversed and fainter colours 
of the secondary bow (if the latter is visible); (d) the relatively 
dark sky between the bows; (e) the general faint illumination 
inside the primary and outside the secondary bow; (/) the 
bows apparently the arcs of concentric circles; (g) the posi- 
tion of the observer with respect to the sun and the bows; 
(/;) (with the teacher's help) the height of the bow and the 
height of the sun. The angular diameter of each bow might 
perhaps also be roughly determined by the teacher, with the 
help of the quicker boys. The succeeding class-work would 
probably consist of (i) the making of written records by the 
boys; and (2) the determination of the fact that the arcs of 
the bows have their common centre on the line joining the 
sun to the eye of the observer. 

Stage 2. Boys 75 to 16. The subject would be taken up 
again in connexion with the study of optical reflection and 
refraction. An artificial bow would be produced by experiment, 
and an explanation based as far as possible on (a) the boys* 
previous recorded observations, (b) the work just done in con- 
nexion with reflection and refraction, and (c) the artificial bow 
would be given of (i) the formation of the bow by refraction 
and reflection; (2) the fact that no two persons can see the 
same bow, since the position of the base of the cone changes 
with the position of the apex; and (3) the fact that a reflected 
bow seen in the water cannot be the " image " of the bow 
seen in the sky. 

Stage j. Boys ij to 18. Simple theory of the bow, from 
a consideration of the principles of interference and the neces- 
sarily constant angular radius of each bow, primary and 
secondary (about 41 and 52). The complete mathematical 
considerations will, naturally, be beyond the ordinary school 
course. 



36 SCIENCE TEACHING 

Or take the subject of capillarity. Here, again, no teacher 
would attempt to exhaust the subject at any one stage. While 
observations of common capillary phenomena ought to be 
made and recorded by quite young boys, theoretical considera- 
tions can be taken up only at later stages. 

Stage I. Observational work in connexion with simple 
experiments: (i) experiments with sponge, blotting-paper, 
sugar, chalk, cotton wick, a piece of cane, &c.; (2) adhesion 
of water to glass effects studied before and after glass is 
polished; (3) capillary elevation and depression plates and 
tubes; (4) study of " drops "; (5) experiments with soap 
bubbles; (6) study of plane soap-films; (7) liquid " skins "; 
(8) experimental illustrations (by the teacher) of the mode of 
formation of liquid figures by the principle of least superficial 
area. 

Stage 2. Study of surface tension and pressure; curvature 
of surface; angle of contact. 

Stage j. Simple mathematical considerations. (Here, 
again, the complete mathematical theory is beyond a school 
course.) 

Present-day Tendencies 

Interesting experiments have become common in the 
teaching of experimental science to boys of about 12 by begin- 
ning the subject, not in the orthodox way of establishing 
principles step by step, but by handing over to a class a piece 
of mechanism,* it may be a bicycle, or perhaps an electric 
bell, telling the boys to discover everything about it they can, 
to consult people and to consult books, and to come prepared 
a week or so later to discuss the whole thing with their teacher. 
Each boy is able to contribute something to the common s*ock 
of facts, and a few boys will probably contribute much. For 
sorting out and arranging the facts, suggestions from the boys 
are called for; and a series of lessons are then arranged for 
working out principles, the known facts being supplemented 

See p. 82 



METHODS 37 

by others derived from experiments which are worked either 
in the laboratory or at the demonstration table. In its way, 
it is the heuristic method over again, but there is no pretence 
that the boy is going to " discover " very much. He may 
discover how the thing works, but most of the why will be 
left to the teacher, and certainly the principles behind the 
how and the why will be mainly the business of the teacher. 
One great advantage of such a scheme for young boys is that 
they are really interested in the business in hand. And even 
older boys immediately show a keen interest when given an 
opportunity to investigate, say, the working of a fiddle, or a 
kaleidoscope, or a pump, or perhaps the working of a reci- 
procating engine, or an internal-combustion engine, or a 
dynamo. The subsequent serious work is understood and 
enjoyed much more than it would be if the subject were begun 
in the orthodox way. And the more that young boys are given 
a chance to make things, especially things that will " work ", 
the more real do such subjects as mechanics and physics become 
to them. 

In America, the " topic " method finds great favour. A 
topic is announced, and the pupils are asked to say what they 
already know about it. In the discussion that follows, questions 
are bound to arise that no member of the class can answer, 
and these are jotted down for investigation. Suppose that the 
topic is air. The class will suggest a score of things at once: 
winds, ventilation, breathing, combustion, the diving-bell, the 
barometer, the pump, the airplane, the composition of air, 
liquid air, compressed air, and so forth. Clearly there is half 
a term's work here on the physics and chemistry of air, even 
when it is decided to postpone certain features that at the 
moment are too difficult. A course is organized accordingly, 
and the boys feel that it is their course. Or perhaps the topic 
chosen is the artificial lighting of the school; the suggestions 
made may include visits to the local generating station, to 
investigate the generation, transmission, and distribution of 
the current; the wiring of the school, lamps, meters and 
measurement, switches, fuses, and so forth. ThtSimmediate 



38 SCIENCE TEACHING 

fruit of these suggestions is an organized course in current 
electricity. But it is a great thing for the boys to feel that it 
is their course, and not a course thrust upon them by authority. 

The plan is not so much a method of teaching as a method 
of approach to a subject. As always, the teacher himself is 
the man at the wheel, but the boys love to think that the ship 
would founder were it not for what they do. 

This American system is said to work well. Boys are 
encouraged to consult books and read up the subject in hand; 
and in every lesson in classroom and laboratory fruitful contri- 
butions are, it is said, often made by the boys. The boys ask 
questions for the teacher to answer; the teacher asks questions 
for the boys to answer it may be at the next lesson. Clearly 
the method has possibilities. The final aim is, of course, to 
work out main principles from accumulated facts, rather than 
to make the facts illustrate principles already established. 

General Remarks on Method 

Whatever general method is adopted, in detail it should as 
far as possible be consistently inductive. Begin with facts, 
facts which are already the common stock of the pupils, then 
with further facts obtained whenever possible from experiments, 
whether these are performed by the teacher or by the pupils. 
The next step will be generalizations from the facts. Thus 
far the work is merely foundational. As soon as the first 
hypothesis is put forward by way of some necessary explana- 
tion, a teacher's real trouble begins, for then both he and his 
pupils are sailing away into cloudland. 

But remember that the inductive method may break down. 
Inductions by beginners are necessarily rather wild. Nothing 
is more common than faulty inductions, and the inductive 
method will inevitably betray the unskilled teacher. The 
discovery of a general law is sometimes the result of ar inspira- 
tion, sometimes the result of a guess, rarely the result of logical 
analysis; and such discovery is hardly reducible to principles 
that can be^Jught. At all events the necessary teaching requires 



METHODS 39 

great skill. Inductions can often be illustrated and verified by 
experiment, but the logic of the laboratory is generally spurious 
stuff. Any sound reasoning is likely to be the teacher's own. 

Remember the inevitable danger of lectures. A preacher is 
supposed to be a teacher, but sermons are proverbially narcotic. 
It takes a Huxley or a Tyndall to lecture and keep the listeners' 
minds in a state of tension. Above all things let your method 
be such as to compel your pupils to think and to reason. Let 
your method be logical. Let the facts and the hypotheses 
which link them be set and seen in a clear picture a puzzle 
picture in which the boys see exactly how the pieces fit to- 
gether. 

Beware of the pseudo method of discovery. " Pour H 2 SO 4 
on granulated zinc, and you will discover that hydrogen is 
given off "! 

Beware of verification methods. " Show that ferrous 
ammonium sulphate contains one-seventh of its own weight 
of iron/' This is simply asking for the evidence to be cooked. 

When a boy works an experiment, keep him just enough 
in the dark as to the probable outcome of the experiment, just 
enough in the attitude of a discoverer, to leave him unprejudiced 
in his observations. 

Do not adopt the heuristic extremist's principle that a 
pupil must not be permitted to take anything second hand. 
Life is too short. 

Do not make the fatal mistake of thinking that all boys 
have an instinct and imagination for making discoveries, or 
can be made first-class workers in the laboratory. In any 
average science class, be satisfied with 25 per cent of a's,. 
50 per cent of /?'s, and 25 per cent of y's, but do not stick 
labels on the y's for all the world to recognize them. 

Teach boys the virtue of recording all mistakes as well as 
successful results. Tell them that all science workers make 
mistakes: that that is almost the normal thing! Faraday, the 
most resourceful experimenter that the world has ever seen, 
said that he learnt far more from his mistakes than from his 
successes. A boy's laboratory note-book containing jio mis- 



40 SCIENCE TEACHING 

takes is never a true record of the work he has done, and it is 
morally wrong to let it be presented as if it were such a j*ecord. 

The pupil's notes should tell a plain tale to people who 
were not present when the record was made, and they should 
be written up in the laboratory, in ink, when the work is in 
progress. 

In the laboratory, a teacher should have everything in 
readiness before a lesson is due to begin, including instructions 
as to the procedure to be followed in all experiments to be 
performed. If these instructions are given orally, they are 
forgotten; dictated, they take up much time; written on the 
blackboard, they are not permanent, and have to be written 
up again for a future lesson. Typed instructions answer best. 

Whatever general method of teaching you adopt, do every- 
thing possible to economize time. It is bad economy it is 
worse, it is sheer waste of time, to say nothing of a lack of 
ordinary teaching intelligence to worry beginners about, say, 
the difference between density and specific gravity, or " pres- 
sure at a point ", or the number of stamens in a flower. 

When devising methods for yourself, remember that good 
method can result only from the constant observation of 
certain broad principles. These include orderly procedure 
throughout a lesson, throughout the work of a term, throughout 
the whole course of instruction; an arrangement of subject- 
matter by which a waste of time and energy may be avoided; 
a distribution of emphasis which will secure the greatest co- 
operation from the pupils and maintain their active interest. 
But do not think that method can be worked out into a body 
of fixed and stereotyped rules of procedure, each applicable 
to its appropriate subject, as a kind of ritual to be observed 
by all teachers in all circumstances. Claims that this can be 
done may be rightly scorned. Teachers are not machines, to 
be turned by a handle. 

At the end of each school year, let every science teacher 
under 35 take stock of the progress he has made in methods 
since his last stock-taking. Let him put his conclusions on 
paper, %nafyse them, and note down for future use any new 



METHODS 41 

basic teaching principles, and any material which will strengthen 
principles previously formulated. In this way let him build 
up his own professional doctrine. The annual progress thus 
recorded may not greatly count unto him for righteousness, 
but at least it ought to count to his professional satisfaction, 
and to provide him with a defensive armour against destructive 
critics, should these ever assail him. 



CHAPTER IV 

Self- training 

Hints to the Beginner 

If you have not been trained but are lucky enough to obtain 
a first post as a junior, in a school with a large science depart- 
ment, under an efficient and experienced senior, all may be 
well. If you are unlucky enough to obtain a post where you 
have to work single-handed, your experience during the first 
year or two will almost certainly be purchased at the expense 
of your pupils. It is only fair to them, and it is greatly in 
your own interest, that you should obtain permission to visit 
two or three schools where well-known science teachers are 
at work, to observe, to ask questions, to make notes. Happily, 
there is amongst science teachers a camaraderie which all be- 
ginners should take immediate measures to share. If you are 
in or near London, attend lectures on method at the London 
Day Training College whenever possible. Make friends with 
Professor Nunn, and when in doubt or difficulty, ask his 
advice. Also make friends with the many clever people on the 
Science Masters' Association, or the Association of Women 
Science Teachers; they will always be willing to help you. 
Become an active member of one of those associations. Read 
The School Science Review regularly; every number contains 



42 SCIENCE TEACHING 

useful articles written by teachers who really know their 
business. Obtain permission from the Board of Education 
to attend one or two summer courses in science teaching; the 
time so spent will be of the greatest possible help. Then there 
is the question of reading. What books can you most profit- 
ably read, to help in your self-training? 

Books to Read and How to Read Them 

The ordinary standard works of science will help but 
little. These you will, presumably, have read already. The 
books to be read now are those which will help you to learn 
to teach. Of these there are two kinds which will help you much: 
(i) school-books written by prominent science teachers; (2) 
original records of the researches of great men of science. 
Books of the first kind should be read right through, not so 
much for the particular sections or particular lessons they 
contain, as for the authors' general method of approaching 
and tackling their subjects from the teaching point of view. 
Read one book through and try to catch the spirit of the author's 
method. Then read a book by a second author, then one by 
a third, and so on. Now compare and contrast the different 
methods. They are bound to be different, though perhaps all 
are excellent. Try to learn something from each, then sit down 
and try to evolve a general method of your own. Do not copy 
other people's methods. If you adopt a general method which 
you have not worked out for yourself, label yourself " second 
class " straight away. Let your general method of teaching 
be your own child, to be nurtured on the best brain-food you 
can give it. The text-books you provide for your pupils' use 
will doubtless subserve a very useful purpose, but do assume 
the captaincy of your own pedagogical quarter-deck. 

Remember that the books in the following list are to be 
read through, not for the sake of the scientific facts they contain 
but in order that you may learn how the authors teach. Some 
of them are quite out of date as regards development of subject- 
matter, bifl for our present purpose that is of no consequence. 



SELF-TRAINING 43 

1. Mr. HolmyarcTs Inorganic Chemistry. 

2. Mr. S. E. Brown 's Experimental Science. 

3. 9ir Richard Gregory's text-books (there is usually a col- 
laborator). 

4. Professor Alexander Smith's Introduction to Inorganic 
Chemistry. 

5. Mr. J. B. Russell's Notes on the Teaching of Elementary 
Chemistry. 

6. Shenstone's Inorganic Chemistry. 

7. Ramsay's Experimental Proofs of Chemical Theory. 

8. Mr. E. A. Gardiner's First Year Course in General Science. 

9. Mr. Willings' General Elementary Science. 

10. Mr. Ivor Hart's Introduction to Physical Science. 

11. Mr. Calvert's Heat. 

12. Mr. Hadley's Electricity and Magnetism. 

13. Professor Ganong's Teaching Botanist. 

14. Smith and Hall's Teaching of Chemistry and Physics. 

All these will repay careful reading, no matter what subject 
of science you have to teach. You will probably learn more 
about methods of science teaching from books on chemistry 
than from books on other subjects. Ramsay's book is open to 
serious criticism. Can you see why? Remember that Ramsay 
was a front-rank chemist. 

The following books are more general, but from the point 
of view of method they are equally valuable. 

15. Huxley's Physiography. 

1 6. Huxley's Discourse on a Piece of Chalk. 

17. Faraday's Chemical History of a Candle. 

1 8. Any half-dozen of the Royal Institution series of Christmas 
lectures to young people. (Those of the last fifteen or twenty years 
are extraordinarily good from the teacher's point of view. They are 
full of useful teaching tips, but it must be remembered that they are 
lectures; for teaching purposes they would have to be largely re- 
modelled.) 

Now we come to original records of the research of great 
men of science, records which tell you exactly how great dis- 
coverers set to work. Teachers who have read these records 
readily admit their great indebtedness to them, especially from 
the point of view of a clear understanding of scientific rqethod. 

( E 72 ) 5 



44 SCIENCE TEACHING 

1. Newton's Opticks. 

2. Faraday's Researches. 

3. Cavendish's Researches. 

4. The Alembic Club Reprints (especially Black's experiments on 
magnesia alba, &c.). 

5. Gilbert White's Natural History of Selborne. 

6. Darwin's Vegetable Mould and Earthworms. 

7. Priestley's Different Kinds of Air. 

8. Davy's The Safety Lamp. 

Lastly we may consider books for particular subjects. 
Suppose chemistry is the special subject you have to teach. 
Select a number of elementary books in the subject, written 
by well-known teachers; note how each writer works out a 
chemistry course, then compare the different schemes, topic 
by topic. For instance; what part do lecture demonstrations 
play in the teaching? what part laboratory work? how are 
these two things associated? how are theoretical principles 
established, inductively or deductively? and so on. The follow- 
ing books, amongst others, are well worth comparing: Mr. 
Holmyard's, Professor Alexander Smith's, Mr. Hooton's, 
Messrs. Dootson and Berry's, Mr. Miller's. The respective 
methods differ radically. Compare them and master them, 
and then you ought to be able to work out a satisfactory method 
of your own. 

Suppose electricity and magnetism is the special subject 
you have to teach. Amongst other books, read the following: 
Dr. Jude's, Mr. Kempson's, Mr. Ashford's, Mr. Carl Hansel's, 
Professor Sylvanus Thompson's (still suggestive in some ways), 
Mr. Hadley's, and some such book as Mr. Hutchinson's 
Technical Electricity. As before, master the principles of each 
writer's methods, then work out a method of your own. Dis- 
regard the fact that a writer may, from the point of view of 
technical knowledge, be hopelessly out of date. We are here 
concerned with method. (Never mind advanced text-books: 
advanced science is easy enough to teach. The real trouble 
is to devise satisfactory methods for boys of 13 to 1 6, whatever 
the science subject may be.) 

Suppose heat, light, and sound is the branch of physics 



SELF-TRAINING 45 

to be taught. Tyndall's books, though nowadays obtainable 
only sqpond hand, should be the first to be mastered; the 
suggestions as to treatment are delightfully fresh still. And 
do not begin to teach light without first reading Mr. W. E. 
Cross's Elementary Physical Optics and noting how easy it is 
to develop the whole subject from the point of view of the 
wave theory. Wave motion is not an easy subject to teach, 
but Fleming's Waves and Ripples is full of useful teaching 
suggestions. Read also Professor Poynting's, Professor Watson's, 
Sir Richard Gregory's, Mr. Brown's, Mr. Willings', Mr. Cal- 
vert's, and Mr. Lewis Wright's books, amongst others; com- 
pare the different methods, but do not copy them. 

Suppose mechanics is the subject. Mr. Ivor Hart's Intro- 
duction to Physical Science and Mr. C. E. Guillaume's Mechanics 
will give the teacher many useful hints for beginning the sub- 
ject. So will Todhunter's almost forgotten books, Mechanics 
and Natural Philosophy. Then the methods of Sir Richard 
Gregory and Mr. Hadley, Mr. Eggar, and Mr. Ashford may 
be compared; and Maxwell's little book Matter and Motion 
is still refreshingly suggestive. Lastly, Mr. Fletcher's article 
in the 1904 volume of the School World should be read through; 
it is probably the best teaching text-book, if text-book we may 
call it, that has been written on the subject. Avoid text-books 
on mechanics that do not develop the subject on an experi- 
mental basis. Mach's Mechanics is the best book for the history 
and philosophy of the subject; it is also the best book for making 
a teacher aware of many possible pitfalls in the handling of 
many of its principles. 

Suppose you are going to give a particular lesson, say in 
chemistry, the subject chosen being the quantitative analysis 
of a bronze coin. Consult two or three authoritative standard 
works, say Professor Hartley's, Professor Thorpe's, and Mr. 
Newth's. The methods may be broadly the same, but it is 
almost always possible to fasten on differences of detail that 
may be of the greatest possible use from the purely teaching 
point of view. Suppose it is a question of, say, the composition 
of ammonia. Would you adopt Mr. Holmyard's or Mr. Hooton's 



46 SCIENCE TEACHING 

or Mr. Newth's or some other writer's method? You should 
not adopt any one of them, not because they are not g<jod, but 
because they are not yours. Get what teaching help you can 
from them all, but let the method you use be the method you 
have worked out for yourself. 

Some writers describe methods which, for teaching pur- 
poses, are very much better than others, even though the latter 
may on the technical side make a stronger appeal to a man 
with an expert knowledge of his subject. In teaching it is a 
safe plan always to make some sacrifice of refinement of 
technique in order to ensure simplicity. An expert chemist 
or physicist may sometimes be tempted to adopt a method 
because of its technical " neatness ", but if this is more diffi- 
cult of apprehension to the pupil than some simpler method 
that may be less attractive to the expert, the latter method 
should be chosen for teaching purposes. In short, in making 
a choice of method, always adopt that method which the pupil 
can follow out and understand clearly. In any demonstration, 
a single point left vague may be fatal. 

Occasionally you may find in a text-book a topic so admir- 
ably worked out that you are inclined to " lift "it. As the 
writer presumably intended it for all the world to use, your 
sin will be a very venial one! Here are a few of such worked- 
out topics, chosen quite at random. Try to improve on them 
if you can. 

1. Professor Alexander Smith: first notions of the qualitative 
and quantitative properties of gases. 

2. Mr. Holmyard: chemical equilibrium. 

3. Mr. Willings: introduction to the reciprocating steam-engine 
and the internal-combustion engine. 

4. Shenstone: composition of water. 

5. Stewart and Gee: the measurement of time. 

6. Mr. S. E. Brown: pressure measurements; experiments with 
Mr. Fletcher's trolley; laboratory experiments in heat, generally. 

7. Sir Richard Glazebrook: first experiments in spectrum 
analysis. 

8. Poynting and Thomson: experiments for illustrating capillarity 
and surface tension (ignore the mathematics, for present purposes). 



SELF-TRAINING 47 

9. Professor Ganong: irritable response of plants. 
10. Sir Frederick Keeble: osmosis and osmotic pressure. 

But never adopt another teacher's method if you can possibly 
improve upon that method. 



CHAPTER V 

Laboratory Directions, Bad and Good 

Directions Open to Criticism 

No part of a science teacher's work is more difficult than 
the preparation of suitable " directions " or " instructions " 
for pupils' practical work in the laboratory. Even for his own 
work at the demonstration table, a previously worked out 
course of procedure will be necessary, and this will be so far 
like the detailed laboratory directions provided for the pupil 
that it will show clearly the succession of steps to be taken 
for the purpose of building up a logically developed scheme. 

We will first give a few examples of laboratory directions 
open to criticism. 

i. Here are successive experiments, taken from an early 
chapter in a book of Experimental Chemistry for Junior Students, 
written by a well-known professor of chemistry. The subject 
of the chapter is AMMONIA. 

" Experiment. Introduce about one c. c. of Hg into a wide test- 
tube; gently warm the metal over a flame, and, directing the mouth 
of the tube away from the person, drop in a fragment of clean metallic 
sodium about half the size of a pea. If the Hg be warm enough, the 
sodium will at once dissolve in it with a little explosion if not, heat 
gently. Then introduce another piece of sodium of the same size, 
and after its solution a third. A silvery white amalgam of sodium is 
thus prepared which retains the metallic lustre. Now pour out the 
warm and still liquid amalgam into about 250 c. c. of a cold saturated 
solution of sal-ammoniac. The amalgam quickly increases to at least 



48 SCIENCE TEACHING 

fifteen times its original bulk, and ultimately becomes a large pasty 
mass, light enough to float on the surface of the liquid. This mass 
can be removed and washed with water; it presents a brillfent and 
metallic appearance, but it is very unstable and soon decomposes, 
evolving ammonia and hydrogen gases, and after some time nothing 
remains but the original mercury. " 

" There is therefore some experimental evidence as to the 
existence of a compound radical ammonium, and the close 
analogies traceable between its saline and other compounds 
and those of potassium and sodium confirm this view. 

" Experiment. Powder half a gram or so of iodine, and add it 
with frequent stirring to 20 c. c. of AmHO solution; allow it to stand 
for half an hour until a black powder has completely subsided, then 
pour away the clear liquid and distribute the black residue on pieces 
of bibulous paper. Put these in some safe airy place to dry. When the 
black substance is dry, a touch suffices to make it explode, when violet 
vapours of iodine are evolved. If small quantities are operated upon 
and reasonable care exercised, the experiment is not attended with 
danger. 

" The black substance is called iodide of nitrogen, and is really a 
mixture of ammonia derivatives. The formula for the chief substance 
is NHI 2 . Analogous bodies are produced by the action of chlorine 
(chloride of nitrogen) and of bromine (bromide of nitrogen); but 
these are amongst the most dangerous explosives known. 

" Many other derivatives of ammonia are known in which various 
groups of elements replace one or more atoms of hydrogen in NH 3 ; 
we may here give the formulae of three of these important bodies: 
NH 2 (C 2 H 5 y (ethylamine); NH(C 2 H 5 )' 2 (diethylamine); N(C 2 H 5 )' 3 
(triethylamine)." 

Such experiments are unsuitable for inclusion in the study 
of ammonia in a beginner's course; they are of no use in 
developing the first principles of the subject; and they are 
too difficult at such an early stage. The directions are not 
detailed enough for beginners, even though they tend to give 
the case away and make the work mere verification. 

2. Next, we take a portion of a chapter on BROMINE, from 
a school chemistry course written by a former well-known 
science master at one of the leading public schools. 



LABORATORY DIRECTIONS 49 



" SOME PROPERTIES OF FREE BROMINE 

" i. Notice the offensive odour of bromine, taking care not to 
expose the eyes to the vapour, and only to smell it when freely diluted 
with air. 

" 2. Place a cork in a bottle containing bromine, and observe 
that the cork is rapidly destroyed. 

" 3. Put a drop of bromine in some water. Notice that it sinks 
(D 3- 1 9), partly dissolving and giving a yellow solution. 

" 4. Cool some bromine water to 4. Crystals having the compo- 
sition Br 2 ioH 2 O?, form. 

"5. Add a drop of bromine water to solution of iodide of po- 
tassium containing starch. Iodine will be liberated and form blue 
iodide of starch. 

" 2KI + Br, - 2KBr + I 2 . 

" 6. Pass hydrogen through a U-tube containing fragments of 
pumice stone soaked with bromine, and provided with a jet; ignite 
the mixture which escapes. Clouds of dense colourless acid fumes, 
resembling those of damp HCl, will testify to the formation of an acid 
fuming gas. This is hydrogen bromide (HBr). 

"7. Place some Dutch gold in bromine. The metal will combine 
with the bromine, but much less readily than with chlorine. 

" 8. Place a strip of Turkey red twill in some bromine water. 
It will be bleached much less rapidly than when chlorine is em- 
ployed." 

With such instructions as these, the pupils would engage 
in mere mechanical routine. They would know exactly what 
is going to happen, or at any rate what is supposed to happen, 
before they performed an experiment. In such circumstances, 
is the average boy likely to engage in active observation? 



3 . The following is taken from an early page in an American 
professor's book written specially for those who are beginning 
organic chemistry. The pupils have, presumably, done a 
certain amount of inorganic work previously, though nothing 
is said about this. 



50 SCIENCE TEACHING 

" CHLOROFORM, CHC1 3 , AND IODOFORM, CHI 3 

" Chloroform or tri-chlor-methane is made by treating ordinary 
alcohol with bleaching powder. The action is deep-seated, involving 
at least three different stages. Chloroform is a heavy liquid, of specific 
gravity 1-526. It has an ethereal odour, and a somewhat sweet taste. 
It is scarcely soluble in water. It boils at 62. It is one of the most 
valuable anaesthetics. 

"Experiment. Mix 550 g. bleaching powder and ii litres 
water in a 3-litre flask. Add 33 g. alcohol of sp. gr. 0-834. Heat 
gently on a water-bath until action begins. A mixture of alcohol, 
water, and chloroform distils over. Add water and remove the chloro- 
form by means of a pipette. Add calcium chloride to the chloroform, 
and, after standing, distil on a water-bath. 

" lodoform, which is extensively used in surgery, is mads by 
bringing together alcohol, an alkali, and iodine. It is a solid substance, 
soluble in alcohol and ether, but insoluble in water. It crystallizes 
in delicate, six-sided, yellow plates. Melting-point, 119. 

" Experiment. Dissolve 20 g. crystallized sodium carbonate in 
100 g. water. Pour 10 g. alcohol into the solution, and after heat- 
ing to 80, gradually add 10 g. iodine. The iodoform separates from 
the solution." 

The directions for these experiments are inadequate. They 
require redrafting and supplementing. To give a mere list 
of properties, without suggesting some experimental method 
of at least verification, is unsatisfactory. 

4. Here is an example from a school text-book of physics. 
Apparently the author is a specialist teacher of the subject. 



" MEASUREMENT OF THE HEAT OF FUSION 

" Let it be required to find approximately the quantity of heat 
that disappears during the melting of one kilogram of ice. This 
quantity is most readily determined by the method of mixtures. 

" Experiment. Weigh out 200 gm. of dry ice chips (dry them with 
a towel), whose temperature in a room of ordinary temperature may 
be safely assumed to be o C. Weigh out 200 gm. of boiling water, 
whose temperature we assume to be 100 C. Pour the hot water upon 
the ice, and stir it until the ice is all melted. Test the temperature of 
the resulting liquid. 



LABORATORY DIRECTIONS 51 

" Suppose its temperature is found to be 10 C. It is evident 
that the temperature of the hot water in falling from 100 to 90 
would yield sufficient heat to raise an equal mass of water from 
o to 10 C. Hence it is clear that the heat which the water at 90 
yields in falling from 90 to 10 a fall of 80 in some manner dis- 
appears. At this rate, had you used i K. of ice and i K. of hot 
water, the amount of heat would be 80 calories. Careful experiments 
in which suitable allowances are made for loss or gain of heat by 
radiation, conduction, absorption by the calorimeter, &c., have de- 
termined that 80 calories of heat are consumed in melting I kilogram of 



Give the instructions to a class of beginners, watch the work 
in progress, then examine the class to find out what they have 
learnt. The instructions are neither adequate nor lucid, and 
the reasoning in the second paragraph is unsatisfactory. The 
words " suppose " and " had you used " are out of place in 
reasoning from experimental data. 

5. Another example from physics, from an American book 
by an American professor and a collaborator. 

" MUSICAL SOUNDS 

" All musical instruments are capable of giving out sound-waves 
of regular intervals. The vibrating spring in the following experiment 
illustrates the action of a tuning fork. 

" Experiment. Take a long straight piece of clock-spring and 
fasten it in a vice or clamp, leaving about 40 or 50 cm. projecting 
horizontally. Set this part vibrating and note the regularity of its 
swings, observing that, like the beats of a pendulum, they take about 
the same length of time, whatever the length, or width, of the swing. 

" Shorten the vibrating part, and observe the effect upon the 
quickness of the swing. Shorten it to 2 or 3 cm., and observe that now 
it gives out a good musical note. 

" A long piece of rubber tubing, fastened at the ends and stretched, 
illustrating the action of the strings in a piano or violin, would be 
found to vibrate regularly with a quickness depending on the degree 
of tension." 

Observe " that they take about the same length of time"! 
Ask a class to work the exneriment. and then to write, down 



52 SCIENCE TEACHING 

how they were able to tell that the swings took about " the 
same length of time ". Contrast the lucid instructions given by 
Stewart and Gee (pp. 186-91 of their book) on me iso- 
chronism of torsional vibrations. The experiment, as above 
described, would certainly not lead to the observation called 
for. 



Directions which may be regarded as Models 

We now give examples of directions which have been well 
thought out, and are exactly what the pupils need in order 
that they may set to work in a really intelligent way. 

i. The first is taken from Mr. Holmyard's Practical 
Chemistry, pp. 101-2. 

" PREPARATION OF NORMAL SALTS 

" Normal salts may be prepared in several ways, the choice of a 
method of preparing a given salt being governed by consideration of 
convenience. 

" Method J. By Neutralization. If the acid and base are both 
soluble, the salt may be obtained by neutralization. Prepare sodium 
chloride in this way: 

" Dissolve about 5 gm. of caustic soda (NaOH) in about 30 c. c. 
of distilled water in a beaker. Pour most of this solution into a clean 
evaporating dish, but reserve a few c. c. in the beaker. Mix some 
of the laboratory * concentrated hydrochloric acid ' with its own 
volume of water, and gradually add the diluted acid to the caustic 
soda solution in the basin. After the addition of every few drops of 
acid, stir the liquid well, and take out a drop of it on the end of a glass 
rod. Test this drop with both blue and red litmus paper. The solu- 
tion will at first be alkaline, i.e. it will turn the red litmus blue. Neu- 
trality is reached when the solution has no decided effect on the litmus 
of either colour. Continue the addition of acid until this stage is 
reached. If you accidentally add too much acid, bring the solution 
back to the neutral point by careful addition of some of the caustic 
soda solution which you have reserved in the beaker. Take care 
to get the solution in the basin exactly neutral; the experiment as a 
whole is so simple that if you fail in this point you must be considered 
to have failed in the experiment altogether. 

" When the solution is neutral, carefully evaporate it over iron 



LABORATORY DIRECTIONS 53 

*auze. Salt is not much more soluble in hot water than it is in cold, 
jo that you must evaporate the solution practically to dryness. Allow 
:he basin to cool, scrape out all the crystals on to a pad of filter paper 
md allow them to dry. 

" Taste the crystals; you will find, if you have been careful in 
leutralization, that they have the flavour of table salt. 

" The equation for the reaction is: 

" NaOH -f HC1 = NaCl -| H 2 O." 

Then follow other methods of preparation, all given with 
'he same happy lucidity. The whole book is worth reading 
through for the sake of its lucidity alone. Many of the experi- 
ments are worth marking down for their own sake. See, for 
instance, Experiment 34 (p. 44) on catalysts. 

2. The second is taken from Smith and Halc's Laboratory 
Outline, p. 65. The letter " R " signifies that the pupil is to 
" refer " to Alexander Smith's Introduction to General Inorganic 
Chemistry. The notes of interrogation signify that definite 
questions have to be answered. 

" SULPHUR 

" (i). In a very dry test-tube, place a very small piece of roll 
sulphur with 2 to 3 c. c. of carbon disulphide and shake. Allow the 
clear solution to evaporate spontaneously (i.e. without the aid of heat) 
in a watch-glass [Flood], and describe the crystals [R 138] (?). 

" (2). In a dry test-tube place about 5 gm. of roll sulphur, melt 
the substance with the least possible application of heat (the material 
must remain pale yellow), and pour into a beaker of cold water. Dry 
some of the product with filter paper, and test its solubility in carbon 
disulphide as in (i). 

" (3). Melt about 10 gm. of sulphur in the same test-tube, and 
heat until it boils (?). Note the changes in colour and fluidity that 
occur. To learn the nature of the substance formed by heating, chill 
the sulphur while it is boiling vigorously, by pouring it suddenly into 
cold water (?). Note the physical state of the product, dry a part with 
filter paper, and examine its solubility in carbon disulphide (?). Set 
the remainder aside for a few days, and then study its appearance and 
solubility again. Keep also the test-tube from which it was poured, 
and examine, at the same time, in both these respects, the sulphur 



54 SCIENCE TEACHING 

which remained adhering to its walls, and was not cooled so 
suddenly (?). Account for the change when sulphur is heated, and 
the differing results of rapid and slow cooling [R 369]. 

" Why are we convinced that none of the changes was due to inter- 
action with the water? 

" (4). Mix in a mortar 2 gm. of iron filings and i gm. of powdered 
sulphur. Transfer to a dry test-tube and heat gently (?). When cool, 
break the test-tube in a mortar and test the black product (?) for solu- 
bility in carbon disulphide." 

3. The following is taken from the List of Exercises in 
Physics, by Professor Hall, required of candidates for admission 
to Harvard. 



" FRICTION BETWEEN SOLID BODIES 

" Apparatus. A spring balance of about 250 gm. capacity; a rec- 
tangular wood-block about 8 cm. X 8 cm. X 4 cm.; a smooth sheet 
of paper about 18" X 12". 

" (i) First consider the velocity of the motion; that is, ask whether 
the force required to keep up a slow steady motion is greater or less than 
that required to keep up a more rapid steady motion. 

" Lay the block upon one of its broad sides, and attach it to the 
spring balance by a thread passing around but not under the block. 
Load the block with weights until the force required to maintain a 
slow steady motion is about 3 oz. Draw the block parallel to its 
grain along the sheet of paper several times with a very slow steady 
motion, and then several times with an equally steady motion two 
or three times as fast. (As the paper is likely to grow somewhat 
smoother under the repeated rubbing, do not make all the slow trials 
first, but change from slow to fast, and fast to slow a number of times.) 

" Record your conclusion as to whether the slow or more rapid 
motion requires the greater force. 

" (2) Next try to find out whether, the total weight being the same 
as before, it is easier or harder to draw the block on a narrower side than 
en a broad side. 

" Use the same block and the same load of weights, pulling it now, 
as before, parallel to its grain. (The sides of the block must always 
be clean, and the broad and narrow sides as equally smooth as 
possible.) 

" Record your conclusion as to whether the broad side or the narrow 
side offers the greater resistance to the motion. 



LABORATORY DIRECTIONS 55 

" (3) Finally , ask what connexion there is between the total mass 
drawn and the force required to draw it. 

" For this purpose, vary the weights placed upon the block, using 
not less than 6 oz. for the least, and as much as 16 oz. for the greatest 
load. 

* ' Add to the load in each case the weight of the block itself, and 
make the record in the following form, W being the load, and b the 
weight of the block: 

W -f- b F (Force required) 



Look for any simple relation between (W -f- b) and F. 

" (In the next part of the investigation, the block was made to 
slide down a sloping board covered with a sheet of paper, arrange- 
ments being made for varying the steepness of the board.) " 

4. The next example is from Mr. J. B. Russell's Notes on 
the Teaching of Elementary Chemistry, intended for young 
beginners. 

" SOME EFFECTS OF HEAT ON SUBSTANCES 

" Heat, one at a time, each of the substances named in the list as 
directed, and try to see all that happens. 

Mercury. Soda. Lead Nitrate. 

Nitre. Borax. Sal-ammoniac. 

Iodine. Red Lead. Blue Vitriol. 

" (i) Describe the substance in such a way that a person after 
reading your description might readily pick out the right substance 
from among the others. 

" (2) Place on a strip of paper, bent in the form of a shoot, about 
sufficient of the substance to cover a shilling, and introduce it into 
a clean dry test-tube without soiling the sides. 

" (3) Heat the tube at first gently and then more strongly. Watch 
all that happens. Allow to cool and examine the residue. 

" (4) Immediately after each experiment write down an account 
of all that you have observed, and in addition answer the following 
questions: 



$6 SCIENCE TEACHING 

" (i) Does the substance left in the tube appear to you to be the 
same as, or different from, the original substance ? 

" (ii) Does any substance appear to leave the tube? if so, describe 
it. 

" (iii) From which of these substances are two, or more, distinct 
substances obtainable?" 



5. Here is an example from Professor Ganong's Teaching 
Botanist. The author claims to present to his class every new 
topic in the form of " a problem so arranged as to be solved 
through proper inductive processes by the pupils' own efforts ". 



" THE ANATOMY OF THE SEED 

" I. (a) Study the outside of the dry Lima Beans; compare several 
specimens and observe what features are common to all and what 
are individual; minutely observe: 

(1) What is the typical shape? 

(2) What is the colour? 

(3) What markings have they? 

" Answer, as far as possible, by drawings made twice the natural 
size; add notes to describe features which drawing cannot express. 

" (6) Remove the coatings from soaked seeds. 

" (i) What effect has the soaking had upon the markings, size, 

and shape? 

" (2) How many coats are there? 
44 (3) Do the external markings bear any relation to the structures 

inside? 
" (4) What shapes have the structures inside, and how are they 

connected with one another? 

k< Answer, as before, by drawings and notes. 

" II. Study fully in the same way the Horse Bean. 
"III. Describe the resemblances and the differences of the Lima and 
the Horse Beans. " 

6. In contrast with the last, we give an example from 
another botanv text-book: what is the contrast? 



LABORATORY DIRECTIONS 57 

'< ENDOSPERMIC SEEDS 

" The Date. Examine a date seed (i.e. the * stone ') Notice the 
deep groove along one side. Scrape the surface on the other side, to 
see the small embryo embedded in the stone (endosperm). Cut the 
stone across at this point; then dip the stone in dilute sulphuric acid 
and apply iodine (test for cellulose). Plant some date-stones in damp 
sawdust or soil, set in a warm place (a heated greenhouse if possible), 
and sketch stages in their germination. Open the stone in some of 
the seedlings, and then notice the softening of the stone and the 
extent to which the cotyledon has grown inside it. Notice 'in sections 
of the stone that the cell-walls become thinner, and that starch appears 
in the young root and shoot, in darkness as well as in light. The 
digestion (conversion into sugar) of the reserve food (cellulose) is 
due to the secretion of a ferment (cytase) by the cotyledon. " 

The suggestions for the systematic examination of the seed 
are excellent, but there is hardly anything left for the pupil 
to discover for himself. He has to " notice " things that he 
is told may be seen. Suppose that he wrote in his note-book: 
" I cut sections of the stone and noticed that the cell-walls 
had become thinner and that starch appeared in the young 
root and shoot. " How could the teacher tell whether the 
hoy had actually done the work and had not spent the half- 
hour in idleness? Why should a boy trouble to notice a thing, 
when it means trouble that it is entirely unnecessary to take? - 
These instructions just fall short of being a model of what 
instructions should be. For the purely private worker, they 
are excellent. 

A few other good examples may be appended: 

7. Glazebrook and Shaw's Practical Physics, pp. 152-5: 
to determine the value of g by observations with the pendulum. 

8. Stewart and Gee's Practical Physics, pp. 24-6: to obtain 
and fix magnetic curves. 

9. Professor Armstrong's Teaching of Scientific Method, 
p. 230: the comparative study of silver and lead (for fairly 
advanced pupils). 

10. Mr. T. G. Bedford's Practical Physics, for present-day 
methods as practised in the Cavendish Laboratory. Half a 



5 8 SCIENCE TEACHING 

dozen of these experiments would give advanced boys a good 
idea of reasonably refined methods of measuremenjs; say, 
linear expansion experiments, determination of the mechanical 
equivalent of heat, determination of the magnifying power of 
the microscope, resonators, the relative capacities of con- 
densers, and the study of the motion of a pendulum. 

Here are a few examples of exceptionally well-written and 
lucid records of observations: Lubbock's Ants, Bees, and 
Wasps, pp. 176-81; Sir R. Lankester's Science and Education, 
pp. 128-9 (for Tyndall's explanation of the optics of a wet 
towel), and pp. 164-5 (f r tne process of repair in a severed 
Achilles tendon); the examples given in The Writing of Clear 
English, pp. 123-70. For a well-written-up account of a topic 
treated historically, see Mr. G. H. Wyatt's story of the Baro- 
meter, with references to Galileo, Torricelli, and Pascal, in the 
School World, for May, 1914. 



CHAPTER VI 

A Common Cause of Failure 

First Illustrative Example: Boyle's Law 

A common cause of failure, especially at the demonstration 
table, is due to one or both of two things: (i) the main purpose 
of the investigation has not been made clear to the pupils; 
(2) the pupils are unprepared by previous training for the new 
lesson in hand. 

We may illustrate the point, first, by reference to the usual 
" verification " of Boyle's law. Obviously the pupil must 
already be familiar with (a) the nature of a ratio, and (b) fluid 
pressure. 

It is not unusual to find the experimental results from a 
Boyle's law apparatus tabulated under p, v, and pv, for the 



A COMMON CAUSE OF FAILURE 59 

teacher to point out that pv is constant, and that therefore the 
pressure is proportional to the volume, and to leave it at that, 
although the pupils may never in their lives have had a lesson 
on ratio and proportion. Boyle's law is too difficult a subject 
for a first lesson in proportion. The notion of a ratio and of 
proportion must already be clearly apprehended, or the lesson 
on Boyle's law is bound to be ineffective. 

One or two simple cases of inverse ratio might suffice by 
way of introduction. For instance: 

i man can build a wall in 64 days. 
.' 4 men can build a wall in 16 days. 
.'. 1 6 men can build a wall in 4 days. 
.' 64 men can build a wall in i day. 

Such a simple illustration is useful, despite its inherent absurdity 
in practical life. The boy sees that the products of the numbers 
of men and days are constant; that a ratio composed of any 
pair of selected terms from the first column is equal to the 
inverted ratio of the corresponding pair of terms in the second 
column. Now graph the result and make boys familiar with 
the general form of the rectangular hyperbola (the name is of 
no consequence). Of course all this is unnecessary if in algebra 

the boys have already reached the stage of graphing y . 

But it is fatal to approach Boyle's law until the boys have a 
clear, if elementary, notion of inverse proportion. 

In the next place, the problem involves the comparison of 
balancing columns of fluids a liquid against a gas. It is an 
application of the principles of fluid pressure, and these prin- 
ciples must therefore have been studied already and clearly 
understood. Boyle's law itself, as a new thing, is quite enough 
for boys to have to understand in one lesson. The previous 
lessons on fluid pressure would probably include: 

1. The ordinary U-tube: the common level of the surfaces 

of the water columns in the two arms. 

2. Ditto, the U-tube having arms of different bores. 



6o SCIENCE TEACHING 

3. Ditto, Pascal's vases: the heights of the columns are the 

same, whatever the volumes. 

4. Water balancing mercury in a U-tube; how the densities 

may be compared by measuring the vertical heights 
above the " surface of separation ". Dwell on the 
fact that the mercury in the bend, below this parti- 
cular surface level, would remain in equilibrium if 
the liquid columns above were removed, and that 
therefore these two columns must balance each other. 

5. The inverted U-tube (Hare's apparatus). Show why 

the columns balance: the full atmospheric pressure 
is the same on the liquid surfaces in the two beakers, 
and the reduced atmospheric pressure is the same 
on the surfaces of the two liquid columns. Vary the 
the form of the apparatus by using tubes of different 
bores, irregular tubes, and tubes out of the vertical. 
The result is always the same if vertical heights are 
measured: this measurement in terms of vertical 
heights is the important point. (It is unnecessary to 
develop Pascal's principle mathematically at this 
stage.) 

6. The mercury barometer: again merely an affair of 

balancing columns a column of mercury balancing 
a column of air measured vertically from the same 
surface level. 

By this time the pupils ought to be prepared to understand 
the usual procedure of a Boyle's law investigation. 

But how to begin? 

Perhaps in this way. I take an ordinary gas jar with a 
well-fitting piston. I push down the piston and so press the 
contained air into a smaller volume. The farther I push down, 
the harder the work becomes. Is there any relation between 
the amount of pressure I exert and the volume of the air under 
the piston? How can we investigate this? Suppose I push 
down the piston until I have halved the original volume of 
air and then measure the pressure I am exerting; then press 



A COMMON CAUSE OF FAILURE 61 

down again, until I have halved the remainder, and again 
measur^ the pressure; and so on. Would this tell me what I 
want to know? Yes. But how am I to measure the pressure? 
that is the question. Here is the plan that Boyle devised. 

And so on. 

The boy now knows exactly what the investigation is to be 
about. And he is already familiar with the elementary prin- 
ciples of fluid pressure and with the principle of inverse ratio. 
There is thus just one new thing for him to learn, viz. how to 
use his knowledge of fluid pressure to find the relation between 
p and v. When he has found this relation, he will recognize 
it as an old friend, viz. the relation of inverse ratio. 

The fragment of the rectangular hyperbola sometimes 
graphed from the values experimentally obtained is seldom 
recognizable for what it is, and is of no value if deductions 
are to be drawn from it. 

That Boyle's law is only an approximation would be men- 
tioned to a Fifth Form and would be explained in a Sixth, 
but would not be mentioned to a Fourth. 



Second Illustrative Example: The Law of Charles 

We may select for discussion the procedure laid down by 
Professor William Ramsay in his little book Experimental Proofs 
of Chemical Theory for Beginners* It begins: 

" Expansion of Gases by Heat. Law: all perfect gases, 
when heated, expand -%}$ of their volume, measured at o C., 
for each rise of i C. (Law of Charles). Required to prove this 
law approximately for air, between the temperature of the room 
and the boiling-point of water." 

Then follows a description of the apparatus used (the usual 
300 c. c. round-bottomed flask heated in a pot of boiling water), 
and details of the experiment. These details are as exact, 

* This curiously misnamed book should be in the possession of every science 
teacher. The experiments for verifying laws are particularly well chosen. But 
of course we cannot " prove " theory. We may perform an experiment to verify 
a law, or to confirm the possibility of the truth of some hypothesis. But if we could 
" prove " theory to be " true ", the theory would become identical with objective 
reality, and cease to be " theory " entirely. 



62 SCIENCE TEACHING 

definite, and practical as might be expected from so eminent 
a chemist. Nothing at all is said, however, by way of ^xplana- 
tion, and even the meaning of x has to be inferred by the 
pupils. Finally, this scheme is given: 

Calculation of results. 

Capacity of flask . . . . . . . . . . a 

Water which has entered on cooling . . . . b 

Volume of air at lower temperature . . . . a b 

Temperature of cold water . . . . . . t 

Temperature of boiling water . . . . . . 100 

Increase of volume measured at o per degree . . 

x 

The relation to be found is as follows: 



Volume of cold air __ 

Volume of hot air . i 

i + - 100 
x 

Multiplying the last two terms by x, 

a b ___ x -f t 
a x + 100 ' 

_ (100 t) a loob 
..* _ . . 

A somewhat similar scheme is given by the writers of 
many other text-books. In order to see if the scheme is 
workable, I have given it to classes of intelligent boys on many 
occasions, but never have I obtained intelligible results. Fairly 
accurate results, from the point of view of mere measurement, 
may be obtained, of course; but a comprehension of the 
purpose and of the procedure, no. 

The first thing to do is to make the pupil understand 
clearly the purpose of the experiment. We may argue in this 
way: 

The purpose of the experiment is to find out the increase 
in volume of a cubic centimetre of air, when it is heated from 
C. to i C. 



A COMMON CAUSE OF FAILURE 63 

We cannot in practice work with a single c. c. of air (about 
a third %f a thimbleful), and we cannot in practice heat the gas 
just from o to i. But we can work with a larger quantity of 
air, and heat it through a greater range of temperature. Will 
this do? Can we obtain from such a result the result we are 
seeking? Let us try. 

Suppose I take a flask which will hold, say, 546 c. c. of air 
at o C., heat it up to 80, and then find that the volume of air 
is 706 c. c. 

Evidently I used 546 times as much air as I really wanted, 
so I must divide the increase by 546; and I heated it 80 times 
as high as was really necessary, so I must also divide the increase 
by 80. 

The increase in volume was 706 c. c. 546 c. c., viz. 
160 c. c. 

Hence I may say: 

Since 546 c. c. at o has increased at 80 by 160 c. c., 

.' i c. c. at o has increased at 80 by ", 

546 

j o u A * o u X 6o c. c i 

and i c. c. at o has increased at i by or c. c.; 

546 X 80 273 

i.e. i c. c. of air, in expanding from o to i, has become I* fa c. c. 

fe call this increase of -^hr the coefficient of expansion. (A 
efficient is merely a number or the fraction of a number, 

used to measure some property of a substance. It is always 

the same for the same substance.) 

It is useful to write the result in the form of an algebraical 

formula: 

Let V = volume of the air at o C. 

Let V* = volume of the air at t C. (the temperature to which 

it is heated). 
Let x = the coefficient of expansion. 

Then x = -J ?. which is exactly like the arithmetical 
V x t' 

fraction above. 



64 SCIENCE TEACHING 

But how is such an experiment to be worked in practice? 
We ask the boys to make suggestions. They will bepuzzled 
and will fail. They will probably say: " If we heat to 100 a 
flask full of ice-cold air, the air will expand and some of it will 
be driven out, but how is it possible to measure this expelled 
portion?" We answer: " It would be so difficult to do it satis- 
factorily that we do not attempt it, and we adopt an entirely 
different plan, a plan that seems to be the reverse of the other. 
We take a flask with air already heated to 100, let it cool down 
to o, then measure the contraction." 

A general preliminary discussion of the actual experiment 
to be performed may now take place, the apparatus being on 
view, and the blackboard being used freely: 

We use a flask, corked, with a short glass tube through 
the cork, and a short piece of india-rubber tubing slipped over 
the glass tube. A clip serves to close the tubing. 

We obtain the volume of the flask by filling it with water 
and measuring this water in a measuring jar. We will suppose 
it to be 300 c. c. The flask is now emptied and dried. 

We now plunge the flask, full of air, into boiling water, 
so that it is completely covered, except the india-rubber tubing. 
The air expands, and some of it escapes. Keep the flask in 
the water for some minutes so that the contained air is heated 
to 1 00 C. Close the clip, and lift the flask out. Now invert 
the flask and immerse it in a vessel of cold water plentifully 
supplied with pieces of ice, and let the contained hot air cool 
to o. Open the clip under water; some of the water rushes 
in, the air having contracted. Pour this water out of the flask 
and measure it in a measuring jar. Suppose it to be 80 c. c. 
Then we know that the volume of the ice-cold air was (300 80) 
c. c., i.e. 220 c. c. 

We may now argue that a volume of 220 c. c. of air at 
o C. would expand to 300 c. c. if heated to 100 C., and we 
can therefore find the coefficient as we did in the imaginary 
case we began with. It seems rather a backward plan of setting 
to work to talk about measuring exoansion. when we realhr 



A COMMON CAUSE OF FAILURE 65 

measured contraction; but if you think about it you will agree 
that oiHr reversal of the process is quite legitimate, and gets us 
over a practical difficulty. 

A preliminary discussion of this kind will make the boy 
familiar with the broad principle to be investigated, and with 
the unusual form of practical procedure in the experiment. 
He need not be worried with such small points as pressure- 
differences at this stage; they can be taken up when the main 
principle has been mastered. 

It is always preferable, at first, to work with the two 
temperatures o and 100. To work at " the temperature of 
the laboratory " for the lower temperature merely serves to 
confuse the main issue and to increase the boy's difficulty of 
always working from first principles. Never use a formula 
in such cases as these if it can possibly be avoided. The main 
thing is to get the physical notion clearly grasped. It is always 
undesirable to let a boy think that when he is working out 
algebra he is doing real physics. 

The alternative plan of using a horizontal narrow glass tube 
with a mercury index, and with a thermometer attached, the 
whole enclosed in a steam-heating glass jacket, is not to be 
recommended. The boy has then to measure lengths only, 
and the all-important idea of volume is apt to be lost sight of. 

Said a boy on being asked a question at the end of a par- 
ticular lesson on this subject: " I am awfully sorry, sir, but 
although I was easily able to follow Mr. X in everything he 
said, I do not understand at all what he meant to teach us." 
Always make quite sure that the boys really do understand the 
nature of the problem they or you are investigating. 



66 SCIENCE TEACHING 

CHAPTER VII 

The Content of the Normal Science 
Course 

The Course up to School Certificate Stage 

The School Certificate examination forms a definite divid- 
ing line between the four or five years' general science course, 
extending from about the age of n| or 12 to that of i6J or 
17, and the more exacting specialized course which usually 
extends over the next two years in preparation for the Higher 
Certificate or for entrance to the universities. The former 
course applies to all pupils, and for some it will be the only 
course. It is therefore desirable that it should be, as far as 
possible, comprehensive and complete in itself. It should not 
consist merely of a preliminary training in preparation for 
advanced work; it should be sufficient to enable a boy to obtain 
some insight into science as a whole, however limited that 
insight may have to be. A treatment on broad lines is thus 
essential. There is no time for the inclusion of much purely 
technical knowledge, and great discrimination is necessary in 
deciding what to include in and what to exclude from this 
preliminary course up to 16^ or 17. 

That physics and chemistry will always be the main 
subjects is inevitable. They form the foundations of all other 
branches of science. But this does not mean that biology 
should be excluded, as is often the case. Biology is an essential 
subject of any school science course. 

The best work before 12 or 13 is not easy to decide upon, 
for boys and girls are not then old enough to face the difficulties 
of a formal training in physics and chemistry. Nature study 
in some form is often begun at the age of 7 or 8, and in its 
broader aspects it may be profitably continued until after 12. 
It waathe fashion for many years to include " physical measure- 



THE NORMAL SCIENCE COURSE 67 

merits " in the preliminary science course, but the subject is 
the concern of the mathematical staff. Time cannot be spared 
for it in the science course. There is a great deal of preliminary 
work that may be done in the laboratory at this stage the use 
of test-tubes and flasks, filtration, decantation, evaporation, 
distillation, the use of the bunsen, the use of the balance, the 
heating of common substances and the alteration in their 
weights, the study of the U-tube, expansion, the simpler 
properties of air and water, and written descriptions of all 
the experiments performed. This kind of work has to be 
done sometime, and it can be done by young children easily 
and profitably. We shall return to the subject in the next 
chapter. 

Then come the four (or five) years of systematic work in 
physics, chemistry, and biology. In some girls' schools, the 
last two of the four or five years is often devoted mainly to 
botany. In other schools the only biology possible is squeezed 
into the summer terms of the two years preceding the School 
Certificate year, and sometimes biology is omitted altogether. 

The old argument that children cannot appreciate experi- 
mental investigation, and cannot therefore profitably begin 
science until about 14!, has rightly been given up. Experience 
shows that physics and chemistry may be begun, at least in 
an informal way, at ia| or 13. 

Those schools that include in the five-years' course nothing 
but elementary mechanics and heat are not treating science 
seriously; indeed, they are treating it contemptuously. No 
boy should leave school thinking that science consists of only 
physics and chemistry, and to turn him out with such a scanty 
fare as one small portion of physics is to turn him out hungry 
indeed. 

It is a common criticism that even in schools where science 
receives serious attention, the four- or five-years' course consists 
of only physics and chemistry. Even so, the subject-matter 
included in the course is often unduly academic, and scarcely 
touches applications to everyday problems. Principles are 
often taught with little or no reference to the phenomena of 



68 SCIENCE TEACHING 

nature they explain, and the course is planned as if the main 
object was to lay the foundations for specialized study at a 
later period. It is a common thing for a boy to be given a 
good training in laboratory methods, and yet to leave school 
without knowing either that he has been devoting four or five 
years to the study of energy under different guises, or that the 
conservation of energy is a great principle underlying the 
whole. There is something seriously wrong in a science teacher's 
outlook when time is spared for lessons on, say, that elegant 
instrument the quadrant electrometer, and still more time is 
spared for lessons on the chlorides of sulphur, and yet no time 
is devoted to the consideration of such things as the thermionic 
valve or common soap. Phenomena which are matters of 
everyday experience should never be lost sight of, and the 
pupils' interest in the world around them should constantly 
be aroused and sustained. 

When the systematic course begins at about 13, let the 
principal aim be not only to provide an exacting mental dis- 
cipline and a training in logical method but also to make the 
pupils acquainted with the principles and foundations of 
common physical phenomena. In any course, a good deal of 
quantitative work will naturally be necessary, for measure- 
ment is the main avenue to exact thought in physical science; 
but do not let time be wasted in emulating the exact measure- 
ments of the National Physical Laboratory. It is a mistake 
to spend time in this way. In planning out a physics course, 
let all branches be fairly represented. The question of syllabuses 
will be dealt with in a future chapter, but it may be said here 
that no elementary physics course is satisfactory that does not 
include considerations of the heating and lighting of the home 
by gas and electricity; electric traction; telegraphy and tele- 
phony including " wireless "; common optical instruments 
including the spectroscope; stringed musical instruments; 
engines, machinery, and mechanism. Do not begin drawing 
up a course by reference to any examination syllabus or to 
any book. Jot down a list of all natural phenomena, discoveries 
and inventions, scientific generalizations and theories, that you 



THE NORMAL SCIENCE COURSE 69 

feel your pupils ought to know and that you can deal with 
in the ti\ne at your disposal. Then sort these out under different 
branches of physics (also of chemistry and biology if you are 
planning a more general course), decide what principles of 
physics must be established for the proper elucidation of the 
phenomena, and arrange these principles in logical order 
according to a possible general development for teaching pur- 
poses. Now turn to your examination syllabuses (unfor- 
tunately, this is necessary), and add to your provisional course 
any examination topics not yet included. Never begin by 
giving pride of place to an examination syllabus. Such a 
syllabus is never drafted for teaching purposes; it is merely 
a medley of topics on which questions may be asked. 

In any elementary course of physics that is to be at all 
satisfactory, the inclusion of mechanics, heat, light, and current 
electricity is essential. Static electricity may be sacrificed 
without much loss; so may, perhaps, the greater part of sound, 
which, with the exception of the monochord and stringed 
instruments, may be postponed for treatment in the later 
Sixth Form course. Wave motion is important enough to be 
regarded as a subject in itself; it goes to the foundations of 
every branch of physics. An elementary treatment of waves 
is possible and is necessary in the Fifth Form; the fuller treat- 
ment must be reserved for the Sixth. 

In drafting a course of instruction in chemistry, reduce all 
purely technological considerations to a minimum, consistent 
with a rational approach to, and development of, the Periodic 
Law. Bring the subject into contact with daily life, and choose 
your topics accordingly. Do not forget that the study of 
equivalents is just a necessary preliminary for establishing the 
laws of combination, that these laws are merely generalizations 
of experimental facts, and that hypotheses and all points of 
theory follow and do not precede those laws. Such topics as 
diffusion, solution, and electrolysis must be included even in 
an elementary course. Avoid quantitative experiments that 
take a long time; they may be reserved for the Sixth Form 
if they are necessary at all. Manufacturing processes are 



7P SCIENCE TEACHING 

always worth touching upon, but never in minute detail. 
Ignore the old dividing line between inorganic and Organic 
chemistry; there is a good deal in organic chemistry that 
should be included in any elementary chemistry course. So 
with chemical processes in the living plant; remember how 
large a part nitrogen plays here. 

The last two years of the four- or five-years' elementary 
course in chemistry is often open to criticism; the sequence 
of topics is too much of a medley, and is not threaded on 
any kind of logical string; the course is dominated by quanti- 
tative work, and yet the purpose of this is not realized as being 
just an essential factor in the rational development of chemical 
theory; facts and hypotheses are confused; reasoning is faulty. 
For instance, the pupils often cannot give a rational account of 
the basic facts that led up to the kinetic hypothesis of gases; 
or explain how Avogadro's hypothesis provides a rational basis 
for the law of Gay Lussac. They cannot fit the facts they have 
learnt into a satisfactory mosaic. As a boy once said to me: 
" All the facts I have learnt in chemistry seem to be just a 
mixture, and not a compound." 

The theory of chemistry must be built up step by step, 
from plane to plane, and the learner must be conscious of the 
building. He must know what facts form the foundations, 
and how each stage of the building rests on the stage below. 
In the whole range of science there is no possible scheme of 
work so logically perfect as the scheme underlying that wonder- 
ful edifice, the Periodic Law. 

Girls' Schools 

Only in recent years has science in girls' schools been 
given a place of equality with other subjects, and even now 
the argument is sometimes used that few girls are capable of 
learning physical science. The consequence is that botany 
still tends to survive as a principal science subject. Twenty 
or thirty years ago, the botany taught was very little more 
than the identification and classification of wild flowers; the 



THE NORMAL SCIENCE COURSE 71 

study of function was not seriously undertaken; and as for a 
preliminary course in physics and chemistry, that was con- 
sidered to be something alien and wholly unnecessary. More- 
over, botany has always been regarded as a soft option for 
girls who (so runs the argument) cannot do mathematics. 
" Botany is such a nice easy subject for the slow girls, and, 
besides, all girls ought to be trained to undertake the dainty 
daily duty of decorating the drawing-room prettily/' It is 
significant that in some schools botany is not even looked upon 
as a branch of science: " She is not good enough for science, 
so she takes botany instead. " 

But botany has now become a very serious subject of study, 
and, in my opinion, it is much more difficult to teach than 
either physics or chemistry. The plant is now treated as a 
living, breathing, feeding, growing thing. The study of 
function rather than morphology now takes the first place; 
and since " life " (whatever that may be) tends greatly to 
obscure the underlying physical and chemical processes, fal- 
lacious reasoning is common even among advanced students. 
As for beginners, they are often hopelessly baffled by the 
complexities of the problems underlying plant biology. Let 
it never be said that botany is an easy subject. It requires 
a thoroughly competent botanist with a large share of teaching 
skill to deal with the subject properly, and it is exceedingly 
doubtful if girls get out of it anything like so good a training 
as boys do from physics and chemistry. 

Some university professors urge that even if girls come to 
them in order to read for botany honours, it does not matter 
at all if the subject has never been begun at school. What 
they specially desire is that the girls shall have been well 
grounded in physics and chemistry. 

If botany is the principal subject taught, its selection must 
be justified: the teaching must provide a rigorous training in 
the methods of scientific reasoning and investigation. 

If the future professional careers of the majority of the 
abler girls are considered teachers of science and mathe- 
matics, teachers of domestic subjects, doctors, dentists, phar- 



72 SCIENCE TEACHING 

macists, factory and sanitary inspectors, welfare workers, and 
health visitors, engineers (there are already several successful 
women engineers) a knowledge of physical science is clearly 
essential, and thus, whether botany is included in a school 
course or not, physics and chemistry must always be taught. 
Or, consider for a moment the future of electricity. In ten or 
fifteen years* time, even village cottages will have complete 
electric installations, and a knowledge of the elementary prin- 
ciples of electrical science will be almost as necessary as a 
knowledge of arithmetic. A school science course which 
ignores electricity altogether, as science courses in some girls' 
schools still do, is assuredly open to serious criticism. In 
short, no adequate excuse can any longer be put forward for 
the omission of physics from the science course of any girls' 
school. 

It is often urged that hygiene is a suitable subject of science 
for girls. The point will be dealt with in a future chapter. So 
will domestic " science ", as it is sometimes called. 

There is much to be said for substituting general biology 
for botany, and including the subject in the Upper and Middle 
Forms of all schools, boys' as well as girls'. Every boy should 
know something of the life history of both animals and plants, 
and something of the physiology of his own body. But what- 
ever may be said about systematic botany, systematic zoology 
and animal dissection is work more suitable for the Sixth Form 
than for younger children. And in any case it has to be borne 
in mind that biology does not lend itself so readily as physics 
and chemistry to experiments of the kind necessary for a full 
appreciation of the principles of scientific method. 

Sixth Form Science 

Boys and girls who have acquitted themselves creditably 
in the School Certificate examination are ready for a more 
intensive study within a limited range. In other words, some 
measure of specialization is now possible. But this speciali- 
2ation should not be narrowed down to a single subject: that 



THE NORMAL SCIENCE COURSE 73 

may come at the university. Rather it should connote a small 
group of allied subjects. For boys, chemistry and physics is a 
favourite group; for girls, botany and chemistry. Boys almost 
always take mathematics as well; girls, sometimes. 

In the Sixth Form, the formal teaching common in the 
Upper Middle Forms is no longer necessary to the same 
extent. The training in method that has already been given 
ought to have prepared the way for the boys and girls now to 
digest much stronger fare. Lectures are no longer entirely 
out of place, especially in the second year of the Sixth Form 
course. Laboratory directions may be given in much less 
detail, and, generally, the pupils may be thrown very largely 
on their own resources. Sometimes they may profitably read 
up a new topic for themselves, different books being suggested 
in order that the topic may be approached from different 
angles; at a later stage one or more teaching periods may 
then be devoted to discussion. But the method to be adopted 
must usually depend on the particular subject taken up. 
Sometimes one or more lessons of the type nominally taken 
in the Fourth or Fifth Form may be advisable, a new topic 
proving so difficult that it is best dealt with step by step at 
the demonstration table, the succession of experiments per- 
formed there by the teacher demanding from the pupils close 
observation and careful reasoning. Sometimes an ordinary 
lecture may be sufficient. Sometimes the pupils may be sent 
straight to the laboratory, there to wrestle in pairs or in small 
groups with the new work. In short, from the teaching point 
of view Sixth Form work will be of a very varied character. 
It may happen that half a term will be devoted to a series of 
experiments, and then a week or two to discussions, to clinch- 
ing arguments, to generalizing experimental data, to estab- 
lishing principles, and so on. In the case of chemistry, all 
pupils will, normally, pursue the same laboratory course, and 
the subject be developed step by step as in the Middle Forms. 
In the case of physics, the limited equipment will generally 
make it necessary for several different types of experiments 
to proceed simultaneously. There is a difference of opinion 



74 SCIENCE TEACHING 

as to the best method of attacking the theoretical side of a 
subject, and of making the best use, to that end, of the pupils' 
experimental results. If the pupils' laboratory course is designed 
merely to verify principles previously demonstrated at the 
lecture table, the value of the course is trifling; there is then 
nothing for the pupils to do but what they have already seen 
done; their hands are engaged but their brains are idle, and 
the work is unworthy of them. There are, however, certain 
types of experiments which demand much ingenuity to carry 
out, even if they have been seen carried out by another person, 
experiments in which the brain has to help the hand in no 
small degree, unless failure is to result. The essential point 
is that during a lesson, whether at the demonstration table or 
in the laboratory, the learner must never become mentally 
stagnant. 

In all Sixth Form work, a high standard of accuracy and 
thoroughness should be consistently demanded. 

Pupils who take biology as a main subject must certainly 
take chemistry as well, and physics ought to be included too. 
It is commonly forgotten how largely physics enters into the 
study of chemistry and biology. Consider, for instance, such 
a simple yet fundamental principle as fluid pressure, which is 
at the bottom of all sorts of chemical and biological experiments. 
A similar remark applies, in fact, to fundamental physical 
principles generally. In all schools, weak physics invariably 
connotes weak science all round. Physics, in its turn, is based 
on mechanics, and, unless elementary mechanics is well 
taught, the physics is bound to be weak. How, for instance, 
can a boy understand the action of a galvanometer unless he 
has previously studied the parallelogram of forces? So generally. 
It is needless to point out that mechanics, in its own turn, is 
based on mathematics. There is a natural sequence in all those 
things that is clamant for recognition. 

It all comes round to this: that if a Sixth Form girl takes 
biology as a main subject, she must have at least an elementary 
knowledge of mathematics, mechanics, and physics, and must 
take a fairly substantial course of chemistry concurrently with 



THE NORMAL SCIENCE COURSE 75 

the biology. A biologist weak in chemistry or physics is a poor 
thing indeed, for the study of function except in a very super- 
ficial way is beyond him. 

We shall return to specialist Sixth Form work in a future 
chapter. 

Non-specialist Sixths 

Boys and girls on the non-science side of the Sixth Form, 
those taking classics, history, and modern languages, will have 
little time for science, but they ought to give up to it two 
or three teaching periods a week. Otherwise, they will on 
leaving school be ignorant of many of the great things that 
the world are interested in and talking about, the things on 
which future civilization largely depends. This remark also 
applies, in no small measure, to those Sixths who are specializing 
in science; the little physics and chemistry, and it may be 
biology, that they can do in two years is, after all, a mere drop 
in the ocean of knowledge of science, and their specialized 
course needs supplementing, if time can possibly be found for it. 

Thus the whole of the Sixth Form might devote, say, two 
periods a week to science of a more general type. There is 
admittedly no time for much laboratory work. Most of the 
ground covered will be covered in the form of lectures, supple- 
mented by directed reading. The lectures should certainly 
not be of the " popular " lecture type. They must be worthy 
of intelligent and well-trained boys and girls. They must be 
given by thoroughly competent teachers, well versed in the 
subject they lecture on; teachers with a broad outlook, and 
abreast of modern research. The lectures should not be dis- 
cursive or fragmentary; evidence should be marshalled, and 
reasoning from that evidence should be rigorous. " The 
lectures must stretch the wits of the cleverer boys." 

Such lectures should deal with scientific questions of general 
interest. In their report, the Prime Minister's Committee sug- 
gested that the following subjects might meet the case, though 
it was not intended that all the schools should adopt the same 
plan: 

(B72) 7 



76 SCIENCE TEACHING 

1 . Cosmical physics and the principles of astronomy. 

2. Physiology and hygiene; bacteriology. 

3. Physical meteorology; weather mapping. 

4. History of astronomy. 

5. History of mechanics. 

6. Development of scientific ideas constitution of matter, 
conservation of energy, evolution, heredity, immunity. 

7. Lives and work of great workers in science. 

8. Bearing of science and invention on industrial progress. 

9. Internal-combustion engine; the dynamo. 

10. The method and philosophy of science, historically treated. 

One or two of these courses might be done fairly exhaustively. 
Alternatively, half a dozen lectures on the subject-matter of 
each course might be given, and the boys be thus provided 
with a large number of topics to think and read about. Experi- 
ments to establish, to elucidate, or to illustrate principles 
should be arranged for whenever possible; and pictorial illus- 
trations, slides for the lantern and for the microscope, and 
photographs should be at hand. There must be plenty of 
private reading, and some essay writing. In some schools, 
the boys themselves give such lectures, sometimes out of 
school hours, and give them extraordinarily well. And why 
not? The important thing is that the lectures must be some- 
thing hard to bite at. They are valueless if they are of the 
type of popular press articles, served up as garnished tit-bits 
from nature's lavish larder. A Sixth Form boy wants his 
teeth sharpened, not his palate tickled. 

Time Allowance 

The minimum time allowance, suggested by the Prime 
Minister's Committee, for the science course preceding the 
School Certificate examination was four teaching periods a 
week in the first year and six teaching periods a week in each 
subsequent year. With less time than this, the course of 
instruction is likely either to be inadequate or to be treated 
superficially. The division of time between the lecture-room 
and the laboratory does not' much matter; that depends on 



THE NORMAL SCIENCE COURSE 77 

the adopted method, and on the man. It is, however, difficult 
to spart so much time for science in most girls' schools, 
especially if the bulk of the teaching has to be done in the 
mornings, though happily the signs of the times are that the 
number of subjects taught may be gradually reduced. In the 
Sixth Form, much more time than that just mentioned will 
be given up to science by those who are specializing, probably 
half the whole working week, in addition to another quarter 
for mathematics. A great deal of time is required for laboratory 
practice in physics, chemistry, and biology. The classical 
and modern studies sections of the Sixth require, in their 
turn, three-quarters of their time for their own special subjects, 
and they are lucky if three periods a week can be spared for 
science. 

In the forms below the Fifth, time is sometimes lost through 
overlapping between science and geography. The teaching of 
the principles of physics and chemistry is the business of the 
science teacher; the teaching of the application of these prin- 
ciples to geography is the business of the geography teacher. 
Time is also sometimes lost through the overlapping of science 
and mathematics. Preliminary physical measurement should 
be included in the mathematical course; so should the nature 
and the plotting of the commoner forms of graph; a science 
teacher giving a lesson on, say, Boyle's law ought not to be 
held up because his boys do not understand the meaning of 
inverse ratio. Time for mechanics in the Upper Middle Forms 
can often be spared from the time given to mathematics; the 
mathematics is strengthened rather than weakened if this is 
done. The time sometimes virtually wasted by keeping mathe- 
matics and mechanics in separate compartments, taught by 
different teachers, might well be spared for biology. 

Time is often lost in the laboratory, especially at the begin- 
ning and at the end of a lesson. This is invariably due to 
faulty organization, not infrequently over such points as the 
distribution of apparatus and the provision of suitable laboratory 
directions. Then, again, laboratory periods are sometimes too 
short, and quantitative experiments are not finished, with the 



78 SCIENCE TEACHING 

consequence that the lesson loses the greater part of its value. 
The copying up of laboratory notes is another commop. source 
of wasted energy. The notes written up at the time of the 
experiment should be final. Copied notes are never faithful 
records of what has been done. 



Directed Reading 

Of course laboratory notes and lecture-room notes are 
altogether insufficient to be representative of the whole of 
the subject taught. Let the pupils read, and teach them how 
to read effectively. Encourage the Sixth Form to read the 
original records of some of the great pioneers of science. 
Help all the boys to acquire the art of reading. Let the old 
catch-words, " weigh, weigh, weigh ", give place to " read, 
read, read ". That weighing and measuring is the very life- 
blood of scientific method is, of course, true, but let the boys 
know all about the thing they are measuring and weighing. 
Too, too often, physics is treated just as if it were mathematics; 
a boy takes readings mechanically, settles down to arithmetic 
and algebra, and labels his work " physics ". I have known 
boys complete a course on " light " without reading any book 
on the subject save one on " geometrical " optics. When 
" light " is thus regarded as just an affair of symbols, it is 
indeed reduced to darkness. 

Make the boys ready and provide them with books to 
read. 



LOWER FORM SCIENCE 79 

CHAPTER VIII 

Lower Form Science 

Nature Study 

We have already said that, until 12 or 13, boys and girls 
are not old enough to face the difficulties of a formal training 
in physics and chemistry, and that nature study, which in some 
form is often begun at the age of 7 or 8, may be profitably 
continued in its broader aspects until at least n or 12, and 
include physiography and astronomical phenomena; also that 
a good deal of preliminary work may be done in the laboratory 
at this stage, especially work of a manipulative character. 

To be effective, nature study must be a study of the real 
thing, and not of blackboard sketches however cleverly these 
may be drawn. The teacher must be something of a born 
naturalist, must have a good stock of first-hand knowledge, 
must be an enthusiastic observer; and if he is a collector, 
so much the better. If he has to train himself, he should read 
the books of well-known naturalists and acquaint himself with 
their methods. Gilbert White's Natural History of Selborne 
is still a classic. This and Darwin's Earthworms, Lubbock's 
Ants, Bees, and Wasps, Professor Miall's books, and a score 
of others mentioned in the library catalogue of the Science 
Masters' Association, should be on the shelves of every teacher 
taking nature study. 

The study of the living plant will naturally occupy a fore- 
most place, and lessons will often be given in the school 
garden or field. The type of work to be done will largely 
depend on the season. Seed germination and bulb-growing 
should form the basis of a good deal of preliminary work. 
Visits should be paid to the field, the hedgerow, the orchard, 
the heath, and the marsh, and wild flowers classified. In a 
town, the local parks must serve, though distant rambles* can 



80 SCIENCE TEACHING 

often be arranged. In the country there are greater opportunities: 
I have known highly profitable visits paid to a farm, 1 for the 
purpose of studying tillage and harvesting operations. The 
soil may form the subject of several lessons; for instance, 
plants that thrive in a heavy soil, in a light soil, or in a chalky 
soil, may be sought and classified. The formation of mould 
is an allied subject. A visit to the local nursery is almost always 
welcomed by the owners; it is a good advertisement for them. 
Much may be learnt there about trees and shrubs as well as 
cultivated flowers. 

Make the young children really keen on the school garden. 

Do not forget that nature study lessons should almost always 
be given out of doors , and this is often possible even in the winter. 
Even during a fall of snow, the children, equipped with hand 
lenses, may be given an impressive lesson on the geometrical 
shapes of snow crystals, examined on the dark coat-sleeve. 
Or a winter lesson may be given on naked trees; for instance, 
the form of a silver birch from base to crown, its branches 
and twigs and the sky behind the tracery; the stout and rugged 
oak, the pyramidal larch, the conical fir, and so on. The barks 
of trees make another interesting lesson: the corky bark of 
the elm, the silvery bark of the birch, the smooth olive-grey 
bark of the beech, the fissured bark of the oak and elm: how 
beautiful they all are. The age of a Scotch fir as inferred from 
its mode of new branching in the spring is another subject 
for an interesting lesson. But there is so much to teach in 
the spring, when nature \vakes up from her sleep, that the 
trouble is to find time to do it all. Let the young children 
learn how to use note-books: their observations they should 
jot down on the spot, and make sketches; these can be worked 
up into material for a future composition lesson. 

But the children's keenest interest is always shown in 
connexion with the study of animal life. Every school should 
possess one or more vivaria an aquarium,* a terrarium, a 
ranarium, a formicarium, and perhaps an aviary. (I have seen 

* For a suggestive article on the construction and stocking of a school aquarium* 
see *7ie Times Educational Supplement for Feb. 17, 1928. 



LOWER FORM SCIENCE 81 

only one school snaillery, and I felt rather doubtful about its 
educational value.) Children take a delight in watching animals* 
movements, and a moving thing naturally tends to quicken, 
their powers of observation. In boarding schools, boys often 
keep their own pets, and in this way collective enthusiasm is 
often aroused, and a great deal of first-hand information 
gleaned. Then, again, lessons on spiders and their snares, 
on silk-worms, silk-spinning and silk-weaving, on the life 
histories of selected insects, and on dozens of other equally 
interesting topics, may be included. A school with access 
to the sea has opportunities for studying crabs and lobsters, 
star fish and sea-urchins, bivalves and univalves, and other 
forms of marine life too numerous to be mentioned. 

London schools have the Zoological Gardens, the Natural 
History Museum, and Kew Gardens at their disposal, and 
willing expert guides may, for the asking, be obtained on the 
spot. A visit to the new aquarium and the new reptile house 
at the " Zoo " is a life -memory to a young visitor. 

Nature study is a term more comprehensive than is always 
remembered. It includes, for instance, a great deal of what 
is commonly called " physiography ". Thus " water and its 
work " suggest considerations of evaporation, clouds, con- 
densation, rain, hail, snow, and ice; springs and rivers; the 
uses of \vater to man; and so on: all such topics lend them- 
selves to an elementary treatment of an interesting character. 
A good deal of elementary astronomy is also within the range 
of young children: the earth as a planet; day and night; the 
seasons; the sun and moon; a few of the chief constellations 
and of the easily recognizable stars; and so forth. 

Of course set " lectures " giving mere information in a 
didactic manner should never be a prominent feature of such 
elementary work. The main thing is to cultivate the children's 
power of observation and to teach them to collect first-hand 
evidence. But lectures should not be ruled out altogether. 
I have heard teachers give lectures to young boys both at the 
" Zoo " and in the Natural History Museum, lectures of a 
strikingly interesting character. With such fine collections to 



82 SCIENCE TEACHING 

discourse upon, why should we object to the lectures? Always 
remember that young children thirst for knowledge. Entourage 
them to read about natural phenomena beyond the reach of 
their personal observation. 

The number of books published on nature study, especially 
on the natural history side, is so great that a selection is difficult 
to make. The selection appearing in the library catalogue of 
the Science Masters' Association may, however, be recom- 
mended without reservation. Amongst newer books the teacher 
might consult one of a particularly suggestive character, namely, 
Boulenger's Animal Mysteries (" night-lights ", " weather pro- 
phets ", " animals and music ", " freaks ", " uninvited guests ", 
" pugilists ", " architects ", " anglers "); and the same author's 
Aquarium Book, and The Naturalist at the Zoo, should be 
available for pupils. 

Elementary Physical Science 

Young children are constantly asking questions. It is 
" how " and " why " all day long. They are eager to know 
how everything works, and the wise teacher turns to account 
this natural curiosity. It is an excellent thing to introduce 
a boy to experimental science, say at about the age of n 
(perhaps at 10, but rarely before this), by giving him a simple 
machine of some sort to take to pieces,* it may be an old clock. 
He soon discovers the object of the toothed wheels, how the 
wheels are pulled round (by weights or by springs), and how 
the pulling is checked. He can now understand gearing, how 
to read meters, and so on. In fact, with very little help he 
learns a good deal about the simple " machines " of mechanics. 
The mechanism of a gramophone is rather too elaborate for 
a small boy, and the spring is too stiff. But a common lock 
he can take to pieces and examine, also a bicycle, and perhaps 
a sewing-machine or an old musical box. A first lesson on 
the balance might be followed up by a lesson on the steelyard 
and an introduction to the lever. The idea of friction may be 

Cf. p. 36. 



LOWER FORM SCIENCE 83 

introduced by telling boys to open a stiff drawer, or to draw 
back a*rusty bolt; they can then learn about the effect of 
lubricants, and be told something about brakes. They pro- 
bably know the bare facts already, in which case the facts can 
be added to and stated more precisely. Such a topic as the 
centre of gravity may be introduced by getting from the boys 
all sorts of illustrations from everyday life; the boys need 
be told but little, except by way of a formal summing up at 
the end of the lesson. It is a great thing to let a small boy 
think that he is providing the facts, and that his teacher is 
playing the part mainly of a listener and a looker-on. Do 
not worry about quantitative work at this early stage, unless 
the arithmetic is of the very simplest. 

Ask a class of young boys how a builder hauls up (i) a 
heavy weight, (2) a light weight, to the top of a building. 
One or more of them will almost certainly be ready with the 
facts, and the essential difference between a pulley-block and 
a fixed pulley (as in the case of a roller blind) may then be dis- 
cussed. By means of such simple illustrations a knowledge of 
the simple " machines " of mechanics may be carried another 
stage forward, though formal mathematical statements must 
wait. 

Then much useful preliminary work may be done in 
connexion with liquids. The measuring jar may be used for 
measuring the volumes of solids. The use of the burette may 
be taught. The U-tube serves as an introduction to the prin- 
ciple that water finds its own level, and an elementary study 
of the school water-supply may follow as an application; a 
first idea of the measurements of the force with which water 
issues from a tap may also be taught. Flotation, and the action 
of a ball-tap may also be considered, but let the principle of 
Archimedes stand over. First notions of air pressure may be 
given, and the principles of the barometer then touched upon; 
but do not bring in the aneroid as a sort of corollary the 
difference is fundamental. Read that sound old book, Tod- 
hunter's Natural Philosophy ; for useful hints on the treatment 
of everyday phenomena, treatment without formalism. IVJost 



84 SCIENCE TEACHING 

boys can understand the general action of a garden syringe, a 
common pump, a diving-bell, a pop-gun, balloons, a parachute, 
a bicycle-pump, a rocket, a spray-producer, a sucker, a common 
air-pump, a bellows, but of course the explanation must be 
kept within the necessarily limited range of their knowledge, 
and always illustrated by experiments that may be understood. 
The fire-engine is a little too difficult for young pupils to 
understand; so, of course, is the airplane. 

First notions of the subject of heat may also be included, 
especially the sections on expansion and thermometry. But 
" coefficients " should play no formal part here. A boy is 
always interested in the general method of measuring a small 
increase in length; he sees at once that a screw of iV-in. pitch, 
if turned through an angle of T ,V (7 of a rotation, must move for- 
wards (or backwards) icVo in. Thus he may be given the 
general notion of the method of determining a coefficient of 
expansion, but he should not be worried with hard terms or 
with arithmetical problems unless, at least, these are very 
easy. Make the boy understand the physical thing and the 
physical action. Let the mathematics wait. 

A little work on change of state, on conduction, on radiation, 
on absorption, may also be included, but only in the form of 
simple qualitative experiment and inferences therefrom. The 
heating system of the school is one obvious thing to utilize 
for a lesson in a preliminary heat course, though, naturally, 
only first general notions can be taught. 

The subject of light will probably be omitted altogether, 
unless the pin-hole camera and what it teaches be made the 
subject of a lesson, perhaps photometry the subject of one or 
two more lessons, and perhaps the common convex lens as 
a burning-glass and as a magnifying glass the subject of 
another. Even the first notions of refraction are, however, 
difficult for young beginners to understand, and reflection 
can be touched upon only very superficially. But in any general 
elementary science course for boys between 12 and 13, the 
first notions of an electric current should always be included 
llpw a current may be produced, and how its effects may 



LOWER FORM SCIENCE 85 

be shown. I have known a boy as young as 10 give a really 
intelligent account of an electric bell intelligent because it 
was not given in the jargon of electrical terminology. 

At about 12, a beginning may perhaps be made with 
chemistry, but this will always be of a very informal kind. 
An examination may be made of such common substances 
as sand, lime, chalk, alum, salt, soda, nitre, magnesia, borax, 
Epsom salts, Glauber salts, sugar, starch, oil, bone, the com- 
moner metals (including alloys), charcoal, alcohol, and turpen- 
tine, and accurate descriptions written. But the descriptions 
must be according to plan. The boys must be taught what 
to look for, and how to describe. The action of heat on some 
of the substances, and the way in which water affects others, 
make useful experiments of a simple kind. The bunsen burner 
and flame may also be included in a beginner's course. On 
the whole, however, it is not advisable to attempt much 
chemistry. What is done should be done with the object of 
affording opportunities to the pupils to learn how to describe 
things, and how to describe changes in things (produced by 
heat and perhaps by the common acids) accurately and clearly. 
This is an essential part of any preliminary training in science. 
Teach the pupils to experiment with small quantities of a 
substance. Teach them to make their own small bulb-tubes 
and to use them for heating substances. 

The science before 12, be it nature study or be it general 
elementary science, should be, before all things, a training in 
observation and a training in accurate and clear description. 
Such training is easily possible. But training in rigorously 
exact inductive reasoning is not possible at such an early stage. 
And, in science, reasoning is mainly inductive in character. 
This is not merely a matter of tying up bundles of facts. Some- 
thing outside the facts has to be supplied by the mind, and 
that is, as a rule, much too difficult for beginners. If, by the 
age of about 12, boys have been trained to observe and to 
describe in accurate language what they have observed, the 
way is paved for more exacting work. Hypotheses and la\vs 
are matters for minds rather more mature. 



86 SCIENCE TEACHING 

On the whole, the best plan is probably to confine the work 
up to ii to plant and animal life, and simple physiography; 
and from n to 12, or a little later, to continue this work and 
to supplement it with introductory physics and chemistry. 

It is advisable to warn children that nature study must not 
become nature pillage. As collectors, children are apt to be 
ruthless. 



CHAPTER IX 

Syllabuses and Schedules of Work 

Examiners' Syllabuses and Teachers' Syllabuses 

We have already pointed out that a science syllabus drawn 
up by an examining body does not pretend to be anything 
more than a number of topics on which questions may be 
asked. No attempt is made to arrange the topics in the order 
in which they are best presented to a class. A teacher will 
cast his eye over it, and so get a general idea of its scope. 
He will then sit down and draft an independent teaching 
syllabus for himself, logically arranged in such a way that 
foundations and principles may be established, points of theory 
worked out, and applications to everyday life included. The 
many gaps in the examination syllabus should thus be filled 
up, for although the examiner will not ask questions on the 
subject-matter that now fills the gaps, this subject-matter is 
essential to the rational development of the course of work. 

Sometimes syllabuses or schedules of work are published 
with the intention of showing what subjects of science might 
be included in a school course if the school could be freed 
from examination requirements, but these also are generally 
unsuitable for a teacher to adopt without rearrangement and 
expsrision. Such syllabuses are occasionally drawn up by 



SYLLABUSES AND SCHEDULES OF WORK 87 

committees or individuals specially asked to draft courses of 
instruction to meet some particular need: it may be a course 
of a more comprehensive character than that usually taught, 
it may be a course which claims to lend itself to improved 
methods. Sometimes these courses are fruitfully suggestive, 
even when they do not square sufficiently with the needs of 
public examinations to make their adoption generally possible. 
Here is such a syllabus of a three-years' course drawn up by 
Sir A. D. Hall, who says: " the spirit in which this course 
should be pursued renders it very unsuitable for formal 
examination ". 



Sir A. D. Hall's Three-years' Course 

First Year, First Term. Properties of Matter: 

Solid, liquid, and gaseous s'ates. 

Density. Identification of materials, e.g. gold, by density deter- 
mination. 

Electricity. The pendulum: determination of time. Galileo. 

Liquid pressure. Archimedes. Flotation. Surface tension. 

Pressure of a gas. Barometer. Boyle. Pumps and siphons. Dif- 
fusion of a gas. 

First Year, Second Term. Chemistry: 

Burning and the products of combustion. Chemical change. Air 
and oxygen. 

Priestley and Lavoisier. Metals and their oxides. The conception 
of elements and compounds. 

Hydrogen. Water. Cavendish's experiments. Solution. 

CO 2 . The isolation of carbon, and its presence in many com- 
pounds. 

Chalk and lime. Black's work. Mortar and cement. 

Nitrogen, ammonia, nitric acid. Rusting and corrosion. 

First Year, Third Term. The Life of a Plant: 

Structure of a seed. Germination. 

The leaf. Transpiration. Photosynthesis. Storage organs. 

The root. Root hairs. Absorption of water. 

Nutrition. Constituents essential to nutrition. 

Flower and seed. Adaptation of plant structure to environment. 



88 SCIENCE TEACHING 

Second Year, First Term. Heat: 

Expansion by heat. Thermometry. 

Distinction between temperature and quantity of heat. Specific 
heat. 

Evaporation. Cooling by evaporation. 

Vapour pressure. Relation between boiling-point and pressure. 

Heat and work. Cooling by expansion of gases. Mechanical 
equivalent. 

Second Year, Second Term. Physics: 

Magnetic bodies. The magnetic field. 

Electric current. Faraday's experiments. 

The simple dynamo. 

Electrical current produced by chemical action. 

Potential and resistance. 

Electrolysis as a reversal of the action of a battery. 

Equivalences in electrolytic action. 

The principle of the conservation of energy. 

Connexion between voltaic and static electricity. 

The nature of a wave. Wave transmission. 

Sound as a vibration. Pitch. Harmonics. 

Light as a wave motion. Reflection. 

Refraction. The prism. Colour. Simple lenses. 

The teacher may approach electricity by way of current 
or by way of the electron. 

Second Year, Third Term. Zoology: 

A broad outline of the animal kingdom. This course should make 
the pupil acquainted with some of the leading differentiae between 
the main groups of animals, and should introduce him to the idea 
of species and classification. Economic considerations should be kept 
in view. It is desirable that every pupil should dissect one animal, 
e.g. a rabbit. 

Some teachers may prefer to take the physiology course 
prior to the zoology. 

Third Year, First Term. Chemistry, second course: 

Carbon as the basal element in the compounds elaborated by 
living organisms. 

Linkages in carbon compounds. Homologous series. Isomerism. 

Alcohol, aldehyde, acetic acid. 



SYLLABUSES AND SCHEDULES OF WORK 89 

Sugars and other carbohydrates. 

Enzymes. Diastase. Alcoholic fermentation. Brewing. 

Yeasts and bacteria. 

The proteins and their hydrolysis by enzymes. 

Colloids and crystalloids. 

Third Year, Second Term. Physiology: 

Circulation. Respiration. Breathing as a form of combustion. 

Muscle. Combustion as the basis of work done by the muscle. 

Digestion. Food values. 

Energy requirements of man; variation with work. 

Nitrogen metabolism and tissue repair. Elimination of nitrogenous 
waste. 

The nervous system. The brain and consciou s nervous actions. 
Reflexes. 

(The cell theory. Somatic and gametic cells. Reproduction.) 

Third Year, Third Term. Botany, second course: 

Asexual reproduction of plants: cuttings, grafts, buds, bulb 
offsets, &c. 

Fertilization. The seedling as a new individual. Variation in seed- 
lings. 

Species and varieties. 

Varieties as a fact. Distinction between congenital and non- 
heritable variations. 

Outline of the theory of natural selection. Inheritance of unit 
characters. 

The course preserves a proper balance amongst the claims 
of physics, chemistry, and biology. It may be regarded as a 
sound general elementary course, though, for teaching purposes, 
a certain amount of " filling up " would be necessary. Indeed, 
this is implied by the course itself. Unfortunately it does not 
quite meet the needs of the requirements of the School Certi- 
ficate examinations. 



"Science for All" 

Another scheme of work which, like the preceding, gets 
right away from examinations and is refreshingly suggestive, 
was drawn up, towards the close of the war, by a committee 
specially appointed to describe the sort of science teaching 



90 SCIENCE TEACHING 

which is suitable to form an essential part of a liberal education, 
and to report on the scope and nature of " Science for All J> 
in Public Schools. In the report the aims of the science course 
to be adopted are stated to be: (i) training in scientific method 
by experimental investigation; (2) conveying useful information 
and fixing it by practical exercises; (3) humanizing the work 
as much as possible by using daily-life phenomena, practical 
applications, machines, agricultural processes, &c., as the 
material. 

" Within the above principles, complete freedom should 
be left to the teacher in accordance with his interest and oppor- 
tunities. He should arrange his own courses, syllabuses, &c.; 
decide what material he employs for any of the above objects, 
and whether he achieves them by ' object ', * subject ', ' pro- 
blem ', or any other method." " The main headings that the 
science should include are given: for convenience these headings 
are grouped under the conventional subjects. But it is the 
humanizing method that is the vital point." 

Then follow numerous headings, with topics worked out 
in considerable detail. When drawing up a science course, a 
teacher may usefully consult this report. He should not adopt 
any of the prescribed syllabuses, any more than he should 
adopt ready-made syllabuses from any other source. But the 
report* is so full of useful hints that every teacher should read 
it. 

"Educational Pamphlet 17 " 

This is a Report on Science Teaching in English Public 
Schools, edited by Mr. O. H. Latter, and published by the 
Board of Education in 1909. It contains a good deal of useful 
information concerning science teaching, and Appendix II 
contains schedules of work from six selected schools. All 
these schedules are worthy of close examination. In particular, 
the reader should pay careful attention to schemes for schools 
" D " and " E ". The former is a physics scheme, with a 

* The Report is signed by Mr. Eggar, Mr. Oldham, and Mr. Vassall. The 
price is 6d. 



SYLLABUSES AND SCHEDULES OF WORK 91 

carefully graded course of work, extending over four years, in 
seven bftmches of physics, viz. mechanics, hydrostatics, light, 
heat, sound, magnetism, voltaic electricity, and frictional 
electricity. The latter is a biology scheme (with further schemes 
in physics and chemistry) of quite exceptional interest. 



The Preparation of a Teaching Syllabus 

The preparation of a satisfactory working teaching syllabus 
is no easy task, especially if the needs of external examinations 
have to be borne in mind. But success depends so much on 
the way in which a course of instruction is approached and 
developed, that it is scarcely possible to give too much care 
to working the course out. 

One of the first difficulties will be to decide how and where 
successive points of theory shall be established. But as in 
nearly all cases these will not be touched upon until accumu- 
lated experimental data demand generalization and the forma- 
tion of hypotheses, the main sequence will be pretty obvious. 
For instance, no attempt may wisely be made to establish 
the Law of Multiple Proportion until a considerable amount 
of definite and satisfactory quantitative experimental work has 
been done with one or more groups of allied oxides. Generally, 
principles will be established simply and solely as the logical 
consequences of generalizations necessarily derived from ac- 
cumulated quantitative results. It is a safe teaching rule to 
let all theory stand over until previous experimental work 
actually calls for it. With an experienced teacher, there would 
be exceptions; but the young teacher should always regard 
such exceptions as a source of possible danger. 

There is a kind of natural sequence in the selection of 
successive topics that probably no teacher could overlook. 
For instance, it would be practically impossible to deal with 
the action of the voltaic cell, or with the photosynthesis of 
plants, until at least a preliminary course of elementary chemis- 
try had been completed; or to deal with the galvanometer, 
before some knowledge of the parallelogram of forces had been 

(E72) 8 



92 SCIENCE TEACHING 

acquired; or with the barometer, before elementary hydro- 
statics had received attention; or with corrections for tempera- 
ture and pressure in experiments with gases, until the baro- 
meter, the thermometer, and coefficients of expansion had been 
considered; or with the kinetic theory of gases, before touch- 
ing upon momentum and energy; or with the intensity of a 
magnetic field, without some previous idea of force and its 
measurement. These and a large number of other points of 
like character will always compel the teacher to adopt the 
same general sequence, though in detail the sequence need not 
follow any particular prescribed form. 

The following teaching syllabus in chemistry was sent to 
me by the late Professor Alexander Smith, whose authority 
as a teacher of the subject carried great weight in the United 
States and Canada during the earlier years of this century. 
He told me that it had been used with marked success in many 
American schools. English teachers who have used it have 
told me that their pupils have obtained a particularly clear 
knowledge of chemical theory, successive hypotheses being 
logically established and the whole body of theory being built 
up step by step. This is undoubtedly the outstanding feature of 
the syllabus. Nowadays it would be severely criticized because 
of its exclusively academic character. Far too little attention 
is devoted to the applications of chemistry and to the chemistry 
of everyday life. But from the point of view of the logical 
development of chemical theory, it leaves little to be desired. 

The course is preceded by the usual preliminary course of 
physics, including Boyle's law, expansion, the physical pro- 
perties of gases, calorimetry, &c. But certain points in physics 
are revised when found necessary, as will be seen. 

A Teaching Syllabus in Chemistry 

In the earlier portion of this course all formula! and equa- 
tions, all ideas of molecules, atoms, and atomic weights, should 
be avoided. Principles must be established from purely experi- 
mental observations. Theories should be introduced with 



SYLLABUSES AND SCHEDULES OF WORK 93 

extreme caution. A knowledge of the atomic theory is quite 
unnecessary in the earlier stages, even if its introduction during 
those stages could be justified. 

The earlier generalizations will be mainly of a qualitative 
nature; for example: 

1. Chemical changes are accompanied by an alteration of 
physical properties. 

2. There is a production or a disappearance of heat. 

3. There is a necessity for contact; a fine state of division 
is advantageous. 

4. There is an increase of speed with an increase of tem- 
perature. 

5. Changes are often more easily effected by dissolving 
substances in water. 

The whole of the early work should be designed to give a 
knowledge of method. Much of it will therefore be thrown into 
the form of problems. For the solution of these, the teacher 
will provide definite laboratory instructions, which, however, 
must never be so full as to tell the pupil anything that he can 
reasonably be expected to discover for himself. 

The larger proportion of the easier experiments will be 
performed by the pupils. As the pupils acquire more and 
more skill, more and more difficult experimental work may be 
required of them. But certain types of experiments will neces- 
sarily always be performed by the teacher himself. 

1. Examination and accurate description of common sub- 
stances: for instance, sand, lime, limestone, chalk, marble, 
alum, common salt, soda, nitre, magnesia, borax, iron pyrites, 
gypsum, Epsom salts, Glauber salts, sugar, starch, fat, olive 
oil, turpentine, the commoner metals, different woods, charcoal, 
coke, coal, alcohol, vinegar. The obvious properties of these 
substances and the principal uses. (It is essential that pupils 
should be taught how to describe things systematically.) 

2. Common laboratory operations, e.g. decantation, filtra- 
tion, evaporation, distillation. 



94 SCIENCE TEACHING 

3. Action of heat on some of the substances above named, 
and how they are affected by air and water. Ele^nentary 
notions of burning. 

4. Alteration in weight of common substances when heated. 
Gain or loss? 

5. Examination of ordinary tap water. How to purify it. 
Amount of air dissolved in water and how to measure it. 

6. Study of the rusting of iron. Iron not affected by pure 
water or dry air. (The reasoning underlying the investigation 
of this problem is generally very faulty.) 

7. The Common Metals. Experiments to show malle- 
ability, ductility, &c. Relative densities: find, and tabulate. 
Metals good conductors of heat. They combine with an active 
constituent of the air to form a new substance called oxides. 
Show formation of iron scale, copper scale, litharge, magnesia, 
zinc white, &c. 

Iron. Show cast iron, wrought iron, steel. Differences and pro- 
perties. Uses. Action of hydrochloric and sulphuric acids on iron. 

Copper. Properties. Uses. Easily attacked by acids. Verdigris. 

Lead. Properties. Uses. Why used by plumbers? Slowly acted 
on by common water: consequence? (The SH 2 test will come later.) 

Silver. Properties. Uses. How blackened by coal-gas or smoke. 

Zinc. Properties. Uses. Action of acids. Galvanized iron. 

Tin. Properties. Uses. Tinned iron (" tin "). 
Common alloys: brass, bronze, pewter, solder. Coinage and 
jewellery. 

8. Crystallization. Efflorescence and deliquescence. Make 
soda and alum crystals. Prepare zinc sulphate crystals by 
dissolving the metal, the oxide, and the carbonate in sulphuric 
acid. Identify the same substance in each case, and note per- 
centage amount of water of crystallization in each case. 

9. Acids and Alkalis. Neutralization. Salts and their 
formation. General action of dilute hydrochloric, nitric, and 
sulphuric acids on the commoner metals and the oxides of 
metals. Tabulate the results. 

At this stage the more systematic study of the subject will begin. 
The work will be mainly quantitative, and data will be gradually 



SYLLABUSES AND SCHEDULES OF WORK 95 

accumulated for the purpose of establishing the more elementary 
principle! of the theory of Chemistry. 

10. Find the weight of a litre of air. Determine the co- 
efficients of expansion of air (constant pressure and constant 
volume). Reduction to N.T.P. 

11. Oxygen. Preparation, Properties, Identification. Com- 
mon oxides. Weight of a litre of oxygen. Amount of oxygen 
obtainable from mercury oxide and potassium chlorate. 

12. Hydrogen. Tests. Properties. Identification. Com- 
parison with oxygen. Volume displaced by zinc and by mag- 
nesium. (Volume, thence weight.) The product formed by 
burning hydrogen. 

13. Water. Produced by burning hydrogen in air or 
oxygen. Properties. Familiar facts. Composition: (i) Synthesis 
pass hydrogen over red-hot copper oxide; ratio of weights 
of hydrogen and oxygen; (2) Analysis by electric current; 
ratio of volumes of hydrogen and oxygen. Now the relations 
between the composition by weight and the composition by 
volume. Elements and compounds defined. 

14. Make magnesium oxide by calcining the metal, also by 
oxidizing with nitric acid. Identify the same product in each 
case, qualitatively and quantitatively. 

Now collect up the results of the various quantitative experi- 
ments performed, and establish the generalization of Definite 
Proportions by weight. Even the smallest conceivable portions 
of a compound must contain its constituents in definite relative 
proportions. Every body is supposed to be made up of such 
little masses, called molecules. Refer to the electrolysis of water, 
which shows that the molecules are broken up. The smallest 
portions of oxygen and hydrogen in the molecules are called 
atoms. 

15. The volumetric composition of water, showing the con- 
densation from three volumes to two. 

1 6. Nitrogen. Preparation from the air. Physical and 
chemical properties. 

17. Atmospheric Air. A mixture. Proportion of oxygen to 
nitrogen. Proof of presence of water and carbon dioxide in air. 



96 SCIENCE TEACHING 

Diffusion of gases. Respiration. Ventilation. Mutual action of 
air and plants. 

Relation of weight of air to weight of its constituents. 
(Cf. the densities of oxygen and nitrogen with the density 
of air.) 

18. Quantitative Research on Chalk/ Chalk, limestone, 
quicklime, lime water, slaked lime. Volume and weight of 
carbon dioxide expelled from chalk. General quantitative inter- 
relations amongst the different substances. (The success of 
this research depends very largely upon the laboratory direc- 
tions supplied to the pupils.) 

19. Hard and Soft Water. Methods of softening. The 
study of washing soda. Familiar facts. 

20. Carbon. Its different forms; allotropism. Its presence 
in organic substances. Carbon dioxide; the lime-water test, 
and further study of the white precipitate. The common 
carbonates. Relation of washing soda to caustic soda. Action 
of alkalis on grease. 

Carbon monoxide: preparation and properties. 

The quantitative relation between the two oxides of carbon. 

21. Combustion. Flame. The phenomena of burning. 
Products of combustion water, carbon dioxide, and perhaps 
ash. Smoke and soot. The use of tall chimneys. The bunsen 
burner; principle. Luminosity of flame. Lamp chimneys. 
Reduction. Coal gas and its manufacture. Coal gas and air 
an explosive mixture. How not to seek the source of a gas 
leakage. 

22. Nitric Acid. Preparation. Properties. Action of the 
acid on metals. Common nitrates. The acid as an oxidizing 
agent. 

23. Nitrous Oxide. Preparation. Properties. Distinguish 
from oxygen. Experimental determination of its composition. 
Weight of a litre of the gas. 

24. Nitric Oxide. Preparation. Properties. Distinguish 
from oxygen and from nitrous oxide. Experimental deter- 
mination of its composition. Weight of a litre of the gas. 

25. The Five Oxides of Nitrogen. Brief comparative study. 



SYLLABUSES AND SCHEDULES OF WORK 97 

(i part by weight of nitrogen to -57, 1-14, 1-71, 2-28, 2-85 parts, 
respectively, of oxygen.) 

26. The Law of Multiple Proportions. State, and illustrate 
with the group of oxides just studied. Verify further, as suit- 
able data are accumulated. Define combining weights. Symbols. 
One or two simple formula?. Chemical equations, as a short- 
hand registration of experimental facts only. Solution of easy 
chemical problems. 

27. Equivalents. Displace silver in silver nitrate by copper 
and by zinc; displace copper in copper sulphate by zinc and 
by magnesium; tabulate the data and the data of former replace- 
ment experiments (e.g. of hydrogen in sulphuric acid by zinc 
and by magnesium), and state and verify the Law of Reciprocal 
Proportions. (These laws cannot be rigorously established from 
the scanty data available, though the data ought to suffice to 
verify a formal statement of them.) 

28. Elementary Notions of the Atomic Theory. Formulae 
and equations cannot yet be used except as shorthand expres- 
sions of experimental facts. 

29. Acids, Bases, Salts further notions. Tabulate instances 
from experimental work already done. Nomenclature of bases 
and of salts. Hydroxides. Mutual action of acids and bases; 
products of the reactions. 

30. Acidimetry and Alkalimetry. Theory of neutralization. 
Solution. lonization. Double salts. Easy volumetric analysis 
(advantages compared with gravimetric). Indicators. 

31. Chlorine. Preparation. Properties. Energetic attrac- 
tion for metals. Weight of a litre of chlorine. Attraction for 
hydrogen. Bleaching and disinfecting; chloride of lime. 

32. Hydrochloric Acid. Preparation. Properties. Com- 
mon chlorides. Weight of a litre of the gas. Combination of 
chlorine and hydrogen no alteration in volume. Composition 
of hydrochloric acid gas, using sodium amalgam; composition 
represented by a formula. We now know the weight of a 
litre of (i) hydrochloric acid gas, and (2) chlorine; we also know 
that hydrochloric acid contains half its own volume of hydrogen. 
Hence we can deduce the weight of a litre of hydrogen. 



98 SCIENCE TEACHING 

33. Ammonia. Preparation. Properties. Composition by 
volume. Weight of a litre. Solubility in water. Amfnonium 
salts. Composition by weight (known weight of gas passed over 
red-hot copper oxide; water and nitrogen collected). From the 
data thus obtained, calculate the relative volumes of hydrogen 
and nitrogen which can be obtained from ammonia gas; com- 
pare with the experimental result of the composition by volume. 

34. Revise Boyle's law, and law of Charles; remember that 
gases agree as regards physical properties, however much they 
differ in chemical constitution. Collect up results on densities 
and on volumes of gases (water, nitrous oxide, nitric oxide, 
hydrochloric acid, ammonia, &c.), and so lead up to the Law 
of Gay-Lussac. Relation between specific gravities and com- 
bining weights of gaseous elements. Revise the work on the 
composition of water by weight and by volume, and show clearly 
how the experimental determinations of the specific gravities of 
(i) w r ater gas, (2) oxygen, (3) hydrogen, help to establish the 
relation between weight and volume of water gas. 

35. We are now in need of Avogadro's hypothesis. For we 
require an explanation of the facts that led up to the Law of 
Gay-Lussac, and Avogadro's assumption is one possible explana- 
tion, though it may be superseded by another some day. 

36. The atomic theory further developed. The probable 
explanation of the facts underlying the Laws of Definite, 
Multiple, and Reciprocal Proportions. The atom, and atomic 
weight. Relation between " equivalents " and atomic weights. 
Distinguish between facts, laws, hypotheses, and theories. 

37. Chemical Formulae. By analysis we find that silver 
nitrate consists of 63-52 per cent of silver, 8-23 per cent of 
nitrogen, and 28-25 per cent of oxygen (by weight). How the 
empirical formula AgNO 3 may be determined from this analysis. 
Why we write AgNO 3 rather than Ag 2 N 2 O 6 or (AgNO 3 ) n . 
Now establish more rigorously the formula of some such com- 
pound as ammonia, nitrous oxide, or carbon dioxide, the 
densities of which have been determined. Distinguish between 
empirical and rational formulae. Equations; their precise 
significance. 



SYLLABUSES AND SCHEDULES OF WORK 99 

We now begin to group together elements and their com- 
pounds for systematic study, in accordance with the 
principles of the Periodic Law. 

38. The Halogens. Revise the work on chlorine; the 
commoner compounds of chlorine. Bromine and iodine and 
their chief compounds. Fluorine and hydrofluoric acid. 

Comparative study of these four elements. Similarity in 
their physical properties; similarity in their chemical actions; 
their combination with hydrogen; progressive diminution of 
chemical energy with progressive increase of combining weight. 
Curious numerical relationthe combining weight of bromine 
a mean between the combining weights of chlorine and iodine. 
A natural group of elements. 

39. Sulphur. Occurrence in nature. Commercial prepara- 
tion and forms. Effects of heat; allotropism (compare oxygen 
and carbon). Solubility. Attraction for metals; sulphides. 
Hydrogen sulphide; preparation, properties, and composition; 
decomposed by salts in solution, yielding sulphides and acids; 
use. Sulphur dioxide; preparation, properties, and composi- 
tion; solution in water; sulphites; bleaching. Sulphuric acid; 
properties and uses; manufacture; effect of mixing with water; 
action on iron and on copper; common sulphates; normal and 
acid salts; monobasic and dibasic acids. Selenium and tel- 
lurium mentioned. Comparison of oxygen, sulphur, selenium, 
tellurium. A second natural group of elements. 

40. Revise work on nitric acid and the nitrates. Phos- 
phorus; manufacture; physical properties; allotropism; phos- 
phorus and hydrogen; phosphorus and oxygen; phosphates; 
matches. Arsenic, antimony, and bismuth, briefly. Com- 
parison of nitrogen, phosphorus, arsenic, antimony, bismuth; 
chemical resemblances; progressive change in specific gravities 
with increase of combining weights; progressive change from 
strong acid to basic character of the oxides, with increase of 
combining weights. A third natural group of elements. 

41. Revise work on carbon and the carbonates. Silicon; 
occurrence in nature; silicon dioxide; silicates; glass. Chemi- 



ioo SCIENCE TEACHING 

cal resemblance between carbon and silicon. A fourth natural 
group of elements. 

42. Valency. Collect useful facts from old work bearing 
on the subject. Comparison of the number of combining 
weights of hydrogen which unite with one combining weight 
of chlorine, oxygen, nitrogen, carbon; observe that the com- 
bining weights of the elements are able to unite with different 
but definite numbers of combining weights of hydrogen. 
Valency as a characteristic of a definite quantity of an element; 
how this quantity may be regarded as (i) the combining weight, 
(2) the atom. Atomic heat.- Atomic weights generally. The 
atomic theory reviewed. 

43. The Periodic Law (briefly): 

(a) Elements having the same valency agree in other chemical 
characters also. Hence the elements are found in natural groups. 

(b) The gradation of properties in each natural group is also found 
to depend on the combining weights. 

(c) Thus we find that combining weight the most fundamental 
chemical property of matter is the natural basis for the classification 
of all elements. 

(d) Show how, by arranging the elements in the order of their 
combining weights, similar properties reappear at regular intervals. 

(e) Point out the eight natural groups thus identified, and the 
gradation of properties in each. 

44. Study of a few of the Common Metals. The power to 
form basic instead of acid hydroxides is the most distinguishing 
chemical characteristic of the metals, but the gradation from 
distinctly acid to distinctly basic properties is unbroken. A 
logical study of the elements should be based on their natural 
relations shown by the Periodic Law. The following metals 
may be selected for study: sodium, potassium, calcium, mag- 
nesium, zinc, mercury, copper, silver, gold, tin, lead, iron, 
aluminium. The study should include the following topics: 

(a) The chief physical properties. 

(b) The principal chemical reactions. 

(c) The most important compounds. 

(d) Alloys. 

(e) Extraction of metal from ores. 

(/) Useful commercial processes and products. 



SYLLABUSES AND SCHEDULES OF WORK 101 

45. Qualitative Analysis. So far as this is necessary, it 
should be made an adjunct to the study of the metals. As 
far as possible, pupils should be taught to make up their own 
separation tables. Any intelligent pupil can discover for him- 
self how to separate, for instance, the chlorides of mercury, 
silver, and lead, if he has been taught to study the chlorides 
separately. Too often the time spent on qualitative analysis 
is absolutely valueless, the operations being entirely mechanical. 

46. Volumetric analysis further studied, especially in con- 
nexion with the theory of solution. 

47. More difficult quantitative experiments of a typical 
nature to verify principles already established. The pupils 
ought now to have acquired a considerable amount of mani- 
pulative skill and to be prepared to perform experiments 
demanding resource and methods of some refinement. 

For Sixth Forms, such a syllabus would have to be extended, 
probably on these lines: 

48. The Periodic Classification: its extended significance. 
Radioactivity. Isotopes. The modern theory of the structure 
of the atom. 

49. Physical Chemistry. Solution: determination of the 
molecular weight of dissolved substances; electrolysis and 
electrolytic solutions. The rate of chemical change: equili- 
brium; catalysis; dissociation. 

50. Organic Chemistry. Structural formulae. The fatty 
derivatives: general methods of preparation, general properties, 
and methods of finding the constitution of the simpler paraffins 
and their halogen, oxygen, and nitrogen derivatives. Mixed 
derivatives and stereo-isomerism. The aromatic derivatives: 
benzene, its constitution and the preparation, properties and 
structure of its simpler homologues and derivatives. 

51. Modern applications of chemistry. 



io2 SCIENCE TEACHING 

An Approach to Botany, Experimentally 

The following is an outline teaching syllabus which has 
been known to work successfully when botany has been 
developed on an experimental basis. It is assumed that a course 
of nature study is taken in the Lower Forms, and that the 
pupils had then acquired a good working knowledge of plants 
and the parts of plants as things carefully observed; also that 
the pupils have been through fairly substantial courses in 
elementary physics and chemistry, the physics including pres- 
sures, capillarity, diffusion, osmosis, heat, and the spectrum; 
and the chemistry including air and water, chalk and the com- 
mon carbonates; the common acids, oxides, and salts; solu- 
tion and crystallization; sulphur and the common sulphates; 
ammonia; the common nitrates; phosphorus; carbon; the 
solvent action of alcohol; starch and its conversion into sugar; 
and elementary notions of the atomic theory enough to 
enable the pupils to realize the significance of simple chemical 
interactions, and of starch and sugar relations. 

The botany syllabus which follows shows a reasonably 
logical sequence, but in practice, the topics selected must 
depend in some measure on the season of the year. And it 
will often be necessary, at some later stage, to return to a topic 
left incomplete at an earlier stage because of its difficulty. 
The necessary experiments are detailed in most of the newer 
text-books. 

THE SOIL 

1. What the soil is: a store-house of moisture and plant food. 

2. Kinds of soils: clay, sand, loam, gravel, chalk, peat. 

3. Soil and sub-soil. Mechanical analysis of soils. 

4. Clay: properties. Clay and water. Action of lime on clay. 

5. Sand: properties. Relative water capacities of sand and clay. 

6. Soil-water: free, capillary, hygroscopic. 

7. Leaf-mould. Percentage lost on burning. Humus. 

8. Plant food in soil. Sow seeds in a pot of (i) soil, (2) sub-soil, 
(3) sand. Vary again with moist and dry soil and sub-soil. 



SYLLABUSES AND SCHEDULES OF WORK 105 

9. Dwellers in the soil. Earthworms. Micro-organisms: gelatine 
cultures.* 

10. The soil and the plant. Experimental proof that soils can 
store water. Excess of water means deficiency of air. 

11. Cultivation and tillage. Plants need water, air, warmth. Action 
of frost. Ploughing, harrowing, raking, hoeing, mulching. 

12. Field expeditions to study soils and sub-soils. 



PLANT FOOD 

1. Elements essential for healthy growth. Except carbon, these 
are absorbed by the roots, usually in the form of nitrates, sulphates, 
phosphates, chlorides, and silicates of K, Na, Ca, Mg, Fe. 

2. Show by water-cultures that these elements are essential. 
Healthy growth only if solution contains potash, lime, and magnesia, 
combined with nitric , phosphoric, and sulphuric acids, with the trace 
of an Fe salt. 

GERMINATION 

1. Plant seeds in sawdust. Keep some wet, others dry; some cold,, 
others warm; some in the light, others in the dark. Sow seeds in soil 
at different depths, at different dates. Sow large and small seeds* 
Tabulate results of differences in yield. 

2. Sow seeds in chopped sphagnum, in box with glass side. Note 
process of germination. 

3. Where and how (i) water, (2) air, enter seeds. 



ROOTS. PLANT PHYSICS 

1. Roots of seedlings. Their behaviour towards moisture, gravity, 
and light. The clinostat. 

2. Determine region of most rapid growth. The growing point. 
Root-hairs. 

3. Diffusion. Illustrate by experiments with blue litmus and 
acid, copper sulphate and water, alcohol and water. Laws of liquid 
diffusion. Colloids. Dialysis. 

4. Osmosis. Dry raisins in water swell up; fresh grapes in strong 
sugar solution shrink. Experiments to show diffusion of sugar solu- 
tion through bladder or parchment with water. Effects with more 
highly concentrated solutions and at higher temperatures. Experi- 
ment to show osmotic pressure by rise of column of water in tube. 
When diffusion necessarily stops. 

5. Turgidity, i.e. osmotic pressure regulated by the influence of 



104 SCIENCE TEACHING 

the protoplasmic layer. Experiments with pieces of beetroot and 
with strips of dandelion stem. Cf. stiffness of root-hair witk stiffness 
of inflated bicycle tyre; pressure in root-hair due to absorption of 
water. Why this absorption? In root absorption, a large quantity of 
hygroscopic water with dissolved salts passes into root-hair. 

6. Elementary notions of the cell as an osmotic apparatus. 

7. The various forms of roots. 



STEMS AND BUDS 

1. Place cut twigs in coloured water. Trace the stained channels. 

2. Compare the stained bundles in dicotyledons and monocotyle- 
dons. 

3. Functions of stems as water-carriers. Vascular bundles in 
leaves continuous with those in stems: demonstrate. 

4. General structure of stem. Growth in thickness; annular 
rings, rays; hard wood and soft wood; cambium; formation of cork. 

5. Modes of branching. Knots in timber. 

6. Healing wounds in trees. 

7. Formation of roots from cuttings. Budding and grafting. 

8. Climbing stems. Underground stems. Spines, prickles, thorns. 

9. Buds. Examine brussels sprouts and horse-chestnut buds. 
Structure and development. 

LEAVES 

1. Use of the large surface. Structure of veins. 

2. Respiration. Absorption of oxygen and giving out of carbon 
dioxide best shown by germinating seeds. (The reasoning in this 
experiment is often faulty. See Ganong's method * with the 3 
U-tubes.) (Respiration and photosynthesis are antagonistic processes, 
though the latter greatly predominates: hence difficulty.) 

3. Transpiration. Experiments with the potometer. (Transpira- 
tion experiments involve no serious difficulty, but reasoning from the 
results demands care.) 

4. Photosynthesis. This is probably the most difficult process to 
demonstrate satisfactorily, and to reason about logically, in the whole 
range of Botany. A course of experiments must be carefully planned 
to show that starch-making cannot proceed in the absence of either 
light, chlorophyll, carbon dioxide, or water. Tell pupils plainly that 
we are still uncertain of the mode of the actual synthesis of starch.f 

5. Process of nutrition considered as a whole. 

* See p. 198. fSee p. 200. 



SYLLABUSES AND SCHEDULES OF WORK 105 

GROWTH 

1. Urowth under varying conditions (temperature, light, mois- 
ture, &c.). 

2. The auxanometer. Auxographic records and their interpretation. 

3. Irritability. Stimulus and response. 

FLOWERS 

1. The different organs and their functions. 

2. Grow sweet peas and show the sub-varieties of colour and shape 
by selection and cross-fertilization. 

3. Experimental study as to the necessity of stamens and pistil 
if seed is to be produced. 

4. Relations of plant to insect life. 

5. Experimental study of pollination. 

6. Colours and scents, and nectar in flowers. 

7. Floral diagrams. 

8. A few common orders: two or three in detail, half a dozen 
others in outline. The use of a Flora. (It is waste of time to 
devote much attention to mere classification, but the botanist's 
principle of classification must be understood thoroughly.) 

FRUIT AND SEEDS 

1. What has become of each of the parts of the original flowers, 
i.e. sepals, petals, stamens, receptacle, ovary, style, stigma? 

2. Various kinds of fruit; adaptations for dispersal. 

3. Comparative examination of, e.g., apple, cranberry, cherry, 
orange, grape, banana, strawberry. Classification of fruits. The 
chief edible fruits and vegetables. 

4. Structure of seeds. 

TISSUES AND CELLS 

1. Epidermal system: continuous over entire plant? Removable? 
Smooth or with appendage? Any green in the epidermis? 

2. Cortical system: continuous over entire plant? 

3. Fibro-vascular system: conducting and strengthening; con- 
tinuous through entire plant (demonstrate). Order of arrangement 
of bundles in stem, in petiole, in leaf. Branching of bundles. 

4. Storage system. 

5. Systems of tissues: protective (epidermis, cork); cortex; 



106 SCIENCE TEACHING 

strengthening (sclerenchyma); growth (cambium); conducting 
(sieve-tubes, wood vessels); aeration (intercellular passtges and 
stomata); storage (pith, medullary rays). 

6. The cell: cell-wall, protoplasm, cell-sap. 

7. Protoplasm: cell nucleus, plastids or chromatophores, cell- 
plasm or cytoplasm. 

8. Cell-wall: thickening, pits, spiral and annular bands. 

9. Cell-division. 

10. Microscopic examination of tissues. 

PLANT ECOLOGY 

The external factors of the conditions of the life of plants in 
nature. Plants associated with heaths, moors, bogs, mountains, sandy 
districts, chalk downs, maritime regions, sandy beaches and dunes, 
saline marshes, coniferous woods, woods of beech, oak, &c., arable 
land, pasture land, ditch sides, ponds, c. 

THE PINE AND THE FERN 

Life histories. 

ECONOMIC USES OF PLANTS 

Timber, cork, fibres, cotton, paper, dyes, tannins, oils, gums, 
resins, rubbers, starches, sugars, " roots " and " tubers ", green 
vegetables, salads, fruits, nuts, condiments, spices, &c. 

Unless botany is taught experimentally, it has little claim 
to rank as science suitable for schools. Too frequently the 
work done is purely observational. The great difference be- 
tween observation and experiment is that the latter implies 
control of some of the conditions underlying a phenomenon. 
In this way differences are established, and these form the 
very foundation of all scientific reasoning. Mere dissection is 
not experiment; it is only clearing away obstructions for the 
purpose of making observations. 

It is not intended that any of the syllabuses outlined in this 
chapter should be adopted for teaching purposes, though they 
are known to have worked well in practice. They are worth 
reading through carefully, and pondering over critically. 



SCIENCE TEACHERS 107 

CHAPTER X 

Science Teachers as Teachers of 
English 

Is the Technical Terminology of Science Necessary? 

In a particularly suggestive article contributed to Nature 
in February, 1925, the writer said: " We cannot accept for a 
moment the common belief that writers on scientific subjects 
compare unfavourably with workers in other intellectual fields 
in the capacity to express themselves in suitable words, or in 
their appreciation of good English, and we resent strongly the 
supercilious attitude which literary people often present to- 
wards scientific works. " 

If, however, that writer will do as I did,* take down at 
random from his library shelves a score of books written by 
men of science, and examine any page chosen at random from 
any of those books, he will probably have little difficulty in 
finding at least one sentence incorrectly constructed. It is 
not a question of such books being obscure to a layman because 
of the use of technical language; it is rather a question of 
loose constructions, and of phrases and sentences not free from 
ambiguity. It is less a question of poor vocabulary than of a 
failure in nicety of discrimination in the use of ordinary words. 
The faults are those of an education which was allowed to 
drift too soon into a specialist channel. 

Consider the case of a boy who has obtained a " credit ", 
perhaps a " distinction ", in English in his School Certificate. 
Does this connote a standard of English good enough for the 
future science specialist? Most certainly not. The boy has 
not reached a stage when he can be said either to express his 
thoughts clearly and forcibly in written and spoken English, 

* See The Writing of Clear English, pp. 86-108. The sentences quoted and 
reconstructed were taken from books selected and opened at random. 

( E 72 ) 9 



io8 SCIENCE TEACHING 

or to construct his sentences without any possibility of am- 
biguity. When science is taken as a main subject in a Higher 
Certificate examination, the test in English should be exacting, 
and a failure to pass the test creditably should entail a failure 
in the whole examination. 

We ought always to distinguish between the backward state 
of technical education and the wonderful success of technical 
achievement. The great majority of the students in the tech- 
nical institutions have not received a liberal education, and 
most of them are therefore likely, on going out into life, to 
remain hewers of wood and drawers of water. On the other 
hand, many of the world's great technical successes have been 
achieved by men who had received the highest possible liberal 
education before they entered upon a technical career. The 
greatest technical excellence is usually traceable to an all-round 
development of the mind and of the personality. Happily 
there is now a great demand by the technical institutions for 
students who have received an all-round education, and, at 
bottom, this means students with some real mastery and 
appreciation of their mother tongue. 

It is a good thing for older pupils to try to understand 
that there is no necessary divorce between the intellect and the 
imagination, between the analytical and the altruistic faculties, 
between the man of science and the poet. Lucretius expounded 
the atomic theory in one of the finest poems ever written. 
Even so recent a naturalist as the older Darwin did not think 
it incongruous to write his botanical treatise in verse. The 
former distaste which many men who were devoted to the 
humanities felt for science probably became most firmly rooted 
at the time of the great leap forward in scientific discovery 
in the last century, and was largely due to the natural dislike 
of one of the less amiable characteristics of the men of science 
of that time the tendency of such men to speak as if their 
discoveries had torn the last veil from the face of nature. 
Really, of course, this conceit was in the disciples, not in the 
masters. As the years went on, all men of science became 
more and more cautious. One after another, the great scientific 



SCIENCE TEACHERS 109 

generalizations that so startled our grandfathers have been 
found to be but faint images of unimagined truths beyond. 
Early dogmatism has given place to hesitancy. In its own 
way, the insight of a Wordsworth is as keen as the insight 
of a Huxley. Science is rapidly becoming reconciled with 
art and literature. And our older pupils should know this, 
and understand why. 

Science is often accused of an excessive fondness for long 
and ugly words, but it must be remembered that the secrets of 
the universe are not to be revealed in monosyllables. A new 
principle, or a new material, or a new relation, or a new unit, 
must, as a rule, be given a new name; if given an old name, 
old associations quite foreign to the new thing would probably 
become attached to it, with all sorts of consequential ambiguities 
in its future use. The word affinity is an instance of the unfor- 
tunate adoption of an old term. The word suggests kinship, 
sympathy, attraction, ideas which confuse rather than explain 
the nature of chemical affinity. The word law is another un- 
fortunate adoption. 

There is, moreover, a complexity of thought that is pro- 
perly represented by complexity of expression. When a man 
has devoted a life-time to the study of a difficult subject, we 
have no right to expect admission to his new secrets if we 
are unwilling even to take the trouble of learning a few un- 
familiar terms. And the true man of science is never guilty 
of adopting such barbarisms as are sometimes met with in the 
commercial world. Such a term as florigene (" floor-hygiene ") 
is an abomination. The term saltrates is as bad. " Ethyl " 
(the petrol mixture containing a small proportion of " anti- 
knock " substance purporting to be lead tetra-ethyl) is even 
worse. 

Simplicity of Expression in Science Teaching 

It ought not to be difficult for a science teacher to make 
himself intelligible, and to make his lessons easy of compre- 
hension. That he will often find it necessary to introduce 



no SCIENCE TEACHING 

new technical terms is true; that is part of his business. But 
these terms will almost always have a perfectly definite con- 
notation, and their meanings will be free from ambiguity 
because of the absence of old associations. In short, exposition 
in science is ambiguous less often because of the use of technical 
terms than because of the incorrect and inappropriate use of 
ordinary words. 

And yet we must distinguish between the language used 
in teaching science, the language commonly used by specialists 
in science, and the language used for lecturing to the man in 
the street. 

If we desire to tell an audience of ordinary intelligent 
persons that a nebula is found to be a gas and not a collection 
of stars, it is easy to say so in those terms, and to give reasons, 
of a sort, to substantiate our statement; the audience will 
appreciate the fact, wonder at it, and understand it more or 
less. But if in the course of a lecture we tell them that " radia- 
tion involves the unimaginable transformation of the negative 
energy of orbital revolution into electromagnetic oscillations 
in an ether the fundamental properties of which we really 
know nothing about ", or if we recite to them some specially 
selected passage from Lord Haldane's Reign of Relativity, 
how much do the audience understand? Is it possible to 
devise a form of words, within the limits of the vocabulary 
familiar to the audience, which will convey an intelligible 
meaning? Of course not. Esoteric science cannot be cast 
into simple language and served up to the man in the street. 
Its technique must always remain the secret of the expert 
and to the amateur be a sealed book. 

And yet this technique is largely of the nature of mere 
tools, necessary only till clearer knowledge is obtained. We 
shall never teach the man in the street how to follow up his 
" world-lines " in " space-time ", or what is meant by " warped 
space ". Such conceptions as these are admittedly necessary 
for the progress of science, but it is a mistake to attempt to 
explain them to the uninitiated, however simple the language 
and however apt the illustration, if only because an uninitiated 



SCIENCE TEACHERS in 

person will never be able to work them into that part of his 
knowledge which consists of clear and distinct ideas. " Popular " 
science is best confined to the exposition of general principles 
and the broader lines of research. Science made intelligible 
is a thing worth aiming at, but science made easy is almost 
certain to be made unscientific. 

The " popular science " lecturer should remember that he 
must never shirk rigorous reasoning. It is always possible 
that the intellect and the powers of reasoning of the man in 
the street may be quite as robust as his own, except that they 
have developed in other directions. The science of the man 
in the street should be as manly as that of the specialist, but 
it should be more general and simple in the truest sense of 
the word. Many technical details and many fine shades of 
difference will, for the man in the street, remain unknown, 
but that is of little consequence. 

Statements at which a scientific critic would cavil need 
not be shunned if they convey the truth. Preference should 
be given even to a verbal inaccuracy if it conveys the true 
spirit of a thing, rather than to a correct statement which has 
twisted itself into an almost unintelligible form in order that the 
lecturer may be saved from the criticism of scientific purists. 

It is exceedingly difficult to provide the right kind of fare 
in science for the non-specialists in the Sixth Form. Obviously 
such boys cannot work with the specialists; the rapidly and 
increasingly difficult technique being acquired by the latter 
makes that impossible. It has, however, to be borne in mind 
that there is little difference in intellectual power between the 
one set of boys and the other. Whatever science is provided 
for the non-specialists must be exacting science: there must 
be no doubt about the facts presented and there must be no 
loose reasoning. The difference will be largely an affair of 
language a much reduced technical vocabulary. It must not 
be " popular " science. " Science for all " does not mean 
" Science for duffers ". 

See that every technical term used and every common 
term used are really understood. Perhaps this is more easily 



112 

done in science than in other subjects. But nothing is rarer than 
the use of a word in its exact meaning. Ask an ordinary Sixth 
Form history specialist exactly what he means by such terms 
as " constitution ", " liberty ", " free trade ", " national debt ", 
" unearned income ", and cross-examine him on his definitions. 
The chances are that he will bungle badly. Even so, ask an 
ordinary Sixth Form science specialist to define the term 
" anticyclone " (coined by the late Sir Francis Galton in 1862), 
and the chances are at least even that he will say that the prefix 
anti signifies opposition (as in antipodes) instead of alternation 
(as in antiphon). Indeed, quite intelligent people are constantly 
using scientific terms loosely; they have never thought out the 
exact significance of the terms. And yet the terms are much 
easier to define than the terms which form the common stock 
of politicians, or of sociologists, or of historians. How often 
even well-trained Sixth Form science pupils confuse impetus 
and momentum; gravity and inertia] centripetal force and centri- 
fugal force, assuming oppositions and relations that do not 
exist. For instance, they oppose centripetal and centrifugal 
forces as if they were forces in the same sense (see p. 129). 
Hypothesis and theory are sometimes confused, even by writers 
of standing. 

Avoid using the term scientist, even though we are badly 
in need of a general term of some kind " to describe a culti- 
vator of science in general ". We want a word equivalent to 
the French savant or the German gelehrte. " Scientist 5> is a 
hybrid. Professor Armstrong has suggested " sciencer " (cL 
" geographer " and " astronomer "), but the word does not 
come very trippingly to the tongue. The word " scientist " 
is being used more and more by general writers, and doubtless 
its general adoption is only a question of time. Nature never 
uses it, however. Nor does any other reputable authority in 
the world of science. 



SCIENCE TEACHERS 113 

Note -making and Note -taking 

It is of the first importance that a science teacher shall 
be scrupulously careful always to use correct English himself; 
then he can be exacting over his pupils' English. The business 
of a science teacher, or of any other teacher, is to teach English 
as well as his special subject. 

Slovenly English in any form of written work should never 
be accepted from pupils. 

Note-taking is an art that must be taught. Small boys 
cannot be expected to make notes until they have been taught 
how to do it. In the very early stages, notes may be dictated, 
for pattern purposes; and lessons may occasionally be given 
on the way in which notes should be made. It will make 
matters simpler if the pupils have already received or are 
receiving precis exercises in their English lessons. Quite young 
children often make full and accurate records of their nature 
study observations; and one great advantage to be derived 
from nature study as a subject is that a child, having made a 
definite observation, then has to try to record that observation 
in words. Once the child has learnt to do this, half the battle 
is won. A succession of observations, properly classified, is the 
next step, and this is generally easy. 

Records of laboratory work are much easier to make than 
records of a teacher's lecture-demonstration. In the laboratory, 
the boy performs a particular operation and records it. In 
the lecture-room, the teacher, no matter how deliberate he may 
be, probably says five times as much as the boy can take down, 
and it is almost hopeless to expect a boy below the Fifth 
Form to son out the facts and put down those that matter most. 
In the Third and Fourth Forms, it is best for the teacher to 
make a pause occasionally, and so give the class an opportunity 
of recording their notes; a hint or two on the best way of 
handling the particular topic under consideration is not 
always inappropriate. And in these Forms a dictated note is 
often necessary. Formal definitions to be expressed in exact 
language, or difficult points of theory, may always be dictated. 



ii4 SCIENCE TEACHING 

In these Middle Forms, in short, the art of note-taking must 
be gradually taught. In the Fifth, boys may be thrown more 
and more on their own resources, and in the Sixth, entirely, 
though much depends on the training in the Thirds and Fourths. 

The notes made in the laboratory should be final, and never 
written up a second time, unless this is necessary by way of a 
punishment for carelessness. Everything a boy does at his 
bench should be recorded at once in ink, as much care being 
taken as possible. All experimental work yielding unsatis- 
factory results should be honestly recorded: by that means 
a teacher learns exactly what progress his pupils are making. 
Let boys know that the cleverest investigators are constantly 
meeting with failures, and that these failures are really stiles 
on the way towards the goal of success.* Laboratory note- 
books are necessarily rather untidy. The teacher, the inspector, 
and the examiner have been through the same mill, and all 
recognize that some untidiness is unavoidable. But there is 
no excuse for unsystematic or for imperfectly recorded notes, 
especially in the Upper Forms. The notes of a laboratory 
lesson should tell the complete story of all the happenings 
during a lesson period. 

At the demonstration table, the teacher presents the subject 
independently of the text-book used by the boys. His presen- 
tation is perhaps wholly different, and is in any case comple- 
mentary. Whether the boys read up the subject from their 
text-book before or after the lesson (they will sometimes do 
one thing, sometimes the other, according to the subject), 
the demonstration will serve to throw new light upon the diffi- 
culties of the topic under treatment. The boy will see the 
thing from two points of view, though the experimental demon- 
stration will naturally be the view that will strike him most. 
What therefore the boy records in his note-book will matter 
much, and to this end his training in the Thirds and Fourths 
is all-important. 

Speaking generally, then, notes must be original. The 
systematic dictation of notes by a science teacher is a repre- 

* Cf. p. 39- 



SCIENCE TEACHERS 115 

hensible practice. It stamps the teacher at once as either 
inefficient or lazy. When a boy sees an experiment performed, 
or performs an experiment himself, and listens to and takes 
part in the discussion concerning the experiment, the thing 
of all things to impress the whole business on his mind is to 
make him express his thoughts in his own words. That which 
is perhaps half vague and fleeting has then to be given a definite- 
ness, though perhaps this definiteness immediately betrays 
only half apprehension. The thoughts self-expressed show at 
once to what extent the facts taught have been assimilated. 

It is a good thing for the teacher occasionally to circulate 
a fair copy of his own notes of a laboratory experiment or of 
a demonstration-table lesson, always after the pupils have made 
their own record. 

When a boy is writing up an essay on a science subject, 
see that he never copies from his text-book. But this does not 
mean that from time to time he may not be told to mark down 
in his text-book telling sentences, or even short paragraphs, 
especially those concerning definitions, laws, &c., to be learnt 
by heart. These may be introduced in the essays, though always 
in inverted commas. 

Do not expect much logic from small boys. But, in the 
Fifth and Sixth, rigorously logical notes must be invariably 
exacted. 

Teach brevity, lucidity, simplicity. 

In the writing up of laboratory notes, the use of the pro- 
noun in the first person should be forbidden. The teacher 
when giving instructions naturally uses the imperative: " Take 
a test-tube, half fill it with water, and add a few drops of acid." 
The boy when writing up his notes should use the past tense 
of the indicative mood, but omit the pronoun as his teacher 
did: " Took a test-tube, half filled it with water, and added a 
few drops of acid." Never allow boys to adopt the irritating 
plan of using the past passive: " A test-tube was taken, it 
was half filled with water, and a few drops of acid were added." 
Worse still is the present passive: " A test-tube is taken, it is 
half filled with water, and a few drops of acid are added ": 



ii6 SCIENCE TEACHING 

when an experiment is described, surely the description is of 
something already done. Use the active voice whenever possible, 
and strike the object directly. Come to the point at once. 

Teach paragraphing, insetting, and arrangement generally. 
Teach classification and tabulation. Show how notes may be 
best arranged to catch the eye of the reader. 

Diagrams should be diagrams, not elaborate pictures. 
Never use coloured inks, except for biological diagrams. Make 
sketches and diagrams from the things themselves; do not 
copy other people's sketches and diagrams. 

The correction and the marking of pupils' notes is the bug- 
bear of the science teacher. All the books should be thoroughly 
overhauled twice a term, and this is easily possible if the work 
is properly organized. But pupils ought always to have their 
note-books open in the laboratory, so that recent notes can be 
glanced over by the teacher passing round. Never spend time 
over making interlinear corrections in note-books. Use symbols 
to indicate the type of mistakes, and make the boys themselves 
correct the mistakes. 

Instruct pupils to use only the right-hand page of the note- 
book for making notes. The opposite side is useful for further 
notes, perhaps from new text-books or from library books, or 
of revision lessons; also for teachers' notes, for corrections, 
and so forth. Let everything be dated when written. Pupils 
should enter up at once on the left-hand page any criticisms 
made by the teacher when passing round, the entry being 
made opposite the note criticized. The points criticized 
should be indicated in the book by the teacher himself, some 
selected code of symbols being used. A teacher will soon 
know which boys tend to water down his criticisms, and 
this watering down should be forbidden, unless at least it 
refers to the teacher's own petulance of language! A little 
petulance is pardonable when a boy oxidizes magnesium and 
thereby claims to have increased the weight of the metal used 
by 10,000 per cent. 



PART II 

THE DIFFERENT SUBJECTS OF 
INSTRUCTION 

In these chapters considerations are given to the different 
subjects of science usually taught, and suggestions are made 
as to methods of treatment. It will be observed that certain 
subjects do not readily lend themselves to anything of the 
nature of an orthodox training in laboratory procedure; they 
are, therefore, best dealt with in the Sixth Form, where freer 
methods of handling are possible. 



CHAPTER XI 

Mechanics 

Why must Mechanics be included in any 
Science Course? 

The question is sometimes asked if it is really necessary 
to include mechanics in a school science course. To answer 
this question, we may consider some complex phenomenon ,. 
say sound, and analyse it. By comparing the various cases in 
which sounds of all kinds are produced, Herschel found * that 
they all agreed in these points: 

1. The excitement of a motion in the sounding body. 

2. The communication of this motion to the air or other 

medium which is interposed between the sounding 
body and our ears. 

3. The propagation of such motion from particle to particle 

of such medium in due succession. 

4. Its communication, from the particles of the medium 

adjacent to the ear, to the ear itself. 

5. Its conveyance in the ear, by a certain mechanism, to the 

auditory nerve. 

6. The excitement of sensation. 

Now in this analysis we notice that two principal matters must 
be understood before we can have a true and complete know- 
ledge of sound: 

1. The excitement and propagation of motion. 

2. The production of sensation. 

* See Scientific Method, III, xix. 
119 



120 SCIENCE TEACHING 

These, therefore, appear to be the elementary phenomena into 
which the complex phenomenon of sound resolves itself. 

But, again, if we consider the communication of motion from 
body to body, or from one part to another of the same body, we 
shall perceive that it is again resolvable into several other 
phenomena: 

1. The original setting in motion of a material body, or any 

part of one. 

2. The behaviour of a particle set in motion, when it meets 

another lying in its way, or is otherwise impeded or 
influenced by its connexion with surrounding particles. 

3. The behaviour of the particles so impeding or influencing 

it in such circumstances. 

The last two suggest another phenomenon which it 
is necessary also to consider, viz: 

4. The phenomenon of the connexion of the parts of 

material bodies in masses, by which they form aggre- 
gates, and are enabled to influence each other 's motions. 

Thus we see that an analysis of the phenomenon of sound leads 
to the inquiry 

1. Into two causes, viz., 

(a) The cause of motion, 

(b) The cause of sensation, 

these being phenomena which we seem to be unable 
to analyse further, and we therefore set them down 
as simple, elementary, and referable, for anything w r e 
can see to the contrary, to the immediate action of 
their causes. 

2. Into several questions relating to the connexion between 

the motion of material bodies and its cause; for 
example, 

(a) What will happen when a moving body is sur- 
rounded on all sides by others not in motion? 



MECHANICS 121 

(b) What will happen when a body not in motion is 
advanced upon by a moving one? 

It is evident that the answers to such questions as 
these can be no others than laws of motion. 

Lastly, we are led, by pursuing the analysis and considering the 
phenomenon of the aggregation of the parts of material bodies, 
and the way in which they influence each other, to two other 
general phenomena, namely, the cohesion and elasticity of matter; 
and these, again, we may regard as simple elementary phe- 
nomena referable to the immediate action of their causes. 
Almost any physical phenomenon is, ultimately, similarly 
reducible. Mechanics forms the foundation of every branch 
of science, including even biology. A knowledge of its main 
principles is therefore essential to a right understanding of 
whatever science is taught. 

The Teacher of Mechanics 

Until the present century, mechanics was sometimes called 
" applied mathematics " or " mixed mathematics ", and even 
university degrees in mathematics, with mechanics as a chief 
subject, have been given to students who never handled a 
machine or a piece of mechanism in their lives. Formulae 
were evolved from the consideration of a few geometrical 
diagrams having the very slenderest relations to practical life; 
and the rest of the work consisted in applying these formulae 
to the working out of all sorts of tricky problems, most of them 
having little or no relation to realities. " Mechanics ", forsooth! 

Now all this is changed, though several text-books of the 
old type survive. Mechanics is now regarded as a branch of 
physics rather than of mathematics, and a subject to be estab- 
lished on an experimental basis. 

The most successful teachers of mechanics whom I have 
known are those who have had a serious training in a mechanical 
laboratory; who know something of engineering, and are 
familiar with modern mechanism; who are competent mathe- 



122 SCIENCE TEACHING 

maticians; and who have mastered Mach's Mechanics, especi- 
ally Chapters I and II.* Mach's book is universally recognized 
as the book for all teachers of mechanics. It deals with the 
development of the fundamental principles of the subject > 
traces them to their origin, and deals with them historically 
and critically. The treatment is masterly. The book might 
with advantage be supplemented by Stallo's Concepts of Modern 
Physics (now rather out of date from some points of view), 
Karl Pearson's Grammar of Science, and Clifford's Common 
Sense of the Exact Sciences and Lectures and Essays. 

It is of great advantage to a teacher of mechanics to be 
familiar with the subject historically. The main ideas of the 
subject have almost always emerged from the investigation of 
very simple mechanical processes, and an analysis of the history 
of the discussions concerning these is the most effective method 
of getting down to bedrock. 

Who were the great investigators? The scientific treatment 
of statics was initiated by Archimedes (287-212 B.C.), who is 
truly the father of that branch of mechanics. The work he 
did was amazing, but there was then a halt for 1700 or 1800 
years, when we come to Leonardo, Galileo, Stevinus, and 
Huygens; to Torricelli and Pascal; and to Guericke and Boyle. 
For dynamics, we go first to its founder Galileo (falling bodies, 
and motion of projectiles), then to Huygens (the pendulum, 
centripetal acceleration, magnitude of acceleration due to 
gravity), and then to Newton (gravitation, laws of motion). 
The great principles established by Newton have been univer- 
sally accepted almost down to the present time, and, so far 
as ordinary school work is concerned, will continue to be used 
at least during the present generation. 

A boy is always impressed by Newton's argument that since 
the attraction of gravity is observed to prevail not only on the 
surface of the earth but also on high mountains and in deep 
mines, the question naturally arises whether it must not also 
operate at greater heights and depths, whether even the moon 

* Hertz also wrote a Mechanics of the same masterly kind, but there is no English 
translation, so far as I know. 



MECHANICS 123 

must not be subject to it. And the boy is still more impressed 
by the sto'ry of the success of Newton's subsequent investigation. 
Newton's four rules for the conduct of scientific investi- 
gation (regulae philosophandi) are the key to the whole of his 
work, and should be borne in mind by his readers. 

The First Stage in the Teaching of Mechanics 

How do successful teachers begin mechanics with boys of 
about 12 or 13? They usually begin by drawing upon the boys' 
stock of knowledge of mechanism.* Most boys know something 
of mechanism, some will have had enough curiosity to discover 
a great deal, and a few will probably have had experience of 
taking to pieces machines of some sort and of putting them 
together again. This stock of knowledge may be sorted out, 
and the topics classified and made the subjects of a series of 
lessons. By means of an informal lesson on some piece of 
mechanism, an important principle may often be worked out, 
at least in a rough way. 

I have known a teacher give his first lesson on mechanics 
in the school workshop, utilizing the power-driven lathe and 
the drilling machine; another first lesson in the school play- 
ground, an ordinary bicycle being taken to pieces. I have seen 
a model steam-engine used for the same purpose, and I have 
known beginners taken to a local farm to watch agricultural 
machinery at work. In all these instances the boys learnt that 
their new subject seemed to have a very close relation with 
practical life. They were not made to look upon it as another 
branch of mathematics, and a rather difficult branch at that. 

Let the early lessons be lessons to establish very simple 
principles. Never mind refinements and very accurate measure- 
ments. Do not bother about small details, and avoid all compli- 
cations. Let the boy get the idea, and get it clearly. Very simple 
arithmetical verifications are quite enough at this stage. The 
boy's curiosity is at first qualitative; let that be whetted 
first, and then turned into a quantitative direction gradually. 

* See Chapter VIII, Lower Form Science. 
(E72) 10 



124 SCIENCE TEACHING 

Encourage the boy to find out things for himself, and do not 
tell him more than is really necessary. Encouragt him to 
ask questions, but as often as possible answer these by asking 
other questions which will put him on a new line of inquiry. 
Let him accumulate knowledge of machines and machine 
processes. Give him some scales and weights, and a steelyard, 
and tell him just enough to enable him to discover the principle 
of moments, but do not talk at first about either " principle " 
or " moments ". It is good enough if at this stage he suggests 
that 

long arm X little weight short arm X big weight. 

He has the idea, and the idea is expressed in such a form that 
it sticks. Give him a model wheel and axle, give him a hint 
that it is really the lever and the lever-law over again, and 
make him show this clearly. Give him some pulleys and let 
him discover, with the help of one or two leading questions, 
how a small weight may be made to pull up a big weight, 
and let him work out the same law once more, but now in the 
form that what is gained in power is lost in speed. Give him 
a triangular block and an endless chain, let him repeat Ste- 
vinus' experiment, and so discover the secret of the inclined 
plane. Let him use a jack to raise your motor-car (and inci- 
dentally learn something about " work "); now tell him some- 
thing about the pitch of the screw, something about Whit- 
worth's device for measuring very small increases in length, 
something about the manufacture of a Rowlands grating. 
Encourage him to give explanations of mechanical happenings 
in everyday life, and use his suggestions as pegs on which to 
hang something new. 

A term of this kind of work pays. The boy is accumulating 
knowledge of the right sort, and when the subject is taken up 
more formally and with a more logical sequence, rapid progress 
may be made. Once he has been taught to read elementary 
mechanism, it is easy enough to teach him its grammar. 
Surely this is the right sequence. Mechanism must come 



MECHANICS 125 

before njechanics. The mathematics of the subject is a super- 
structure, to be built upon a foundation of clear ideas. 

Of course, if the preliminary work of the preparatory school 
or department has been properly done, the way is paved for 
an earlier treatment of a more formal kind. 



The Second Stage 

The second stage will consist of work of a more systematic 
character, but still work essentially practical, though arranged 
on a logical string. Ideas will now be classified, and mathe- 
matical relations gradually introduced. But the physical thing 
and the physical action must still remain in the front of the 
boy's mind. The mathematics will take care of itself. 

Let the teaching be inductive as far as possible. Obtain 
all necessary facts from experiments, and do not use experi- 
ments merely for verifying a principle enunciated dogmatically. 

The basic principles to be taught are really very few, and 
a boy who knows these thoroughly well can work most ordinary 
problems on them. Mechanics is, after all, largely a matter of 
common sense. The laws of equilibrium, together with the 
ratio of stress to strain, covers almost the whole range of 
statical problems, including those of hydrostatics; while New- 
ton's Laws of Motion cover practically everything else. But 
of course these are basic principles. If they are known, known, 
derived principles are learnt easily enough; if they are only 
vaguely known, derived principles are never really mastered. 

Statics or dynamics * first? Teachers do not agree. There 
is much to be said for beginning with dynamics, first using the 
ballistic balance for studying colliding bodies, and the momen- 
tum lost by one and gained by another; it is then an easy step 
to pass on to the idea of force. But a boy who is led to think 
of a force as something analogous to muscular effort will always 
be in trouble, and in any case he is likely to form a very vague 
idea of acceleration. And, after all, uniform acceleration is 
anything but common in practical life: we nearly always refer 

* The terms kinetics and kinematics are falling into disuse. 



126 SCIENCE TEACHING 

either to falling bodies or to a train moving out from ^ station. 
It is this difficulty that makes many teachers take up statics 
first. Although, at the outset, a boy's working idea of force 
is necessarily crude, a spring balance, for simple quantitative 
experiments, helps to put the boy on the right track, and there 
is much to be said for allowing him to assume, to begin with, 
that weight is the fundamental thing to be associated with force. 
At an early stage he may verify, to his own satisfaction, the 
principles of the parallelogram and triangle of forces, but he 
must be warned that he has not yet " proved " these principles 
and cannot yet do so. But since the parallelogram of forces is 
such a useful working principle, it would be foolish not to 
allow the boy to use it before he can prove it formally. At this 
stage formal proofs are difficult, and it is simply dishonest to 
encourage a boy to reproduce a page of bookwork giving a 
proof of something quite beyond his comprehension, though 
this was common enough thirty or forty years ago. 

Do not employ graphic statics at too early a stage, or the 
real point at issue may be obscured. 

Now as to dynamics. What is the best approach? We 
have already referred to the ballistic balance. Should Atwood's 
machine be used? It may be used, perhaps, for illustrating the 
laws of motion, but not as a practical method of finding . 

Atwood's machine has been superseded by Mr. Fletcher's 
trolley,* by means of which practically the whole of the prin- 
ciples of dynamics may be satisfactorily demonstrated. It 
lends itself to many experiments, all of which provide a space- 
time curve ready made, and, from that, speed-time and acce- 
leration-time curves may be plotted. In a paper read at the 
York meeting of the British Association, Mr. C. E. Ashford 
gave details of a large number of trolley experiments as per- 
formed at Dartmouth, a school where the teaching of mechanics 
is well known to be of a high order. Reference has already been 
made to Mr. Fletcher's own article in the School World for 

* The friction of the trolley may be eliminated either by tilting the plane to 
the necessary angle, or by attaching a weight that will just maintain uniform motion. 
The friction of the pulley over which the thread passes cannot be compensated, 
and it is therefore necessary to use a good pulley. 



MECHANICS 127 

May, 1904. In it he shows how boys may be given sound ideas 
of the physical meaning of the terms, moment of inertia, 
angular momentum, moment of momentum, and therefore of 
moment of rate of change of momentum and moment of force. 
Useful teaching hints may also be found in Mr. S. H. Wells's 
Practical Mechanics and Mr. W. D. Eggar's Mechanics. 

Once the foundations of mechanics have been well and truly 
laid the superstructure may be erected according to traditional 
methods. To leave the subject just as developed in the labora- 
tory would be to leave it unfinished. But the superstructure 
may now be built properly. When necessary formulae have 
been evolved from experiment, the physical things behind the 
formulae have to the boy a reality of meaning which the older 
" methods of applied mathematics " teaching could not possibly 
give him. 

If principles are not understood, proofs have no meaning. 

Throughout the whole of a mechanics course, every oppor- 
tunity should be taken to excite the boys' interest in new 
mechanical inventions. It helps the more academic work 
enormously, and makes the boys feel that the subject is really 
worth taking trouble over. Examples occur on every side 
variable speed gears, transmission gears, taximeters, boat- 
lowering gear, automatic railway signalling, automatic tele- 
phones, the self starter in a motor-car, the kick-starter in a 
motor-cycle, and so on. Some mechanical devices depend, in 
their turn, on electricity, and their place of introduction into 
a teaching course would be determined accordingly. Complex 
mechanisms like the air-plane, the submarine, the paravane, 
should not be wholly forgotten. Boys can read up such things 
for themselves, and perhaps prepare and read papers on them 
to the school science society. 

Hydrostatics 

The mechanics of fluids is an exceedingly difficult subject 
to teach effectively. Even a Sixth Form boy is sometimes held 
up by questions on the barometer or on Dulong and Petit's 



128 SCIENCE TEACHING 

equilibrating columns. The work of Archimedes and Pascal 
for liquids and of Boyle for gases cannot be too we'll done. 
Above all, the U-tube must receive careful attention, and 
especially the surface level above which pressures are compared. 
Do not buy Hare's apparatus from an instrument maker's. 
The standard pattern is always made with two straight tubes, 
of the same bore, fixed vertically. Let the boys make a variety 
of forms of this apparatus for themselves, and work out the 
vertical height law from data as varied as possible. Approach 
the whole subject of hydrostatics from the point of view of 
familiar phenomena, e.g. measure the water pressure from a 
tap in the basement and again from a tap in the top story of 
the school, and see if there is any sort of relation between the 
difference of these pressures and the height of the school. 
Do not try to establish a principle formally until the phenomenon 
under investigation is clearly understood as a physical happening. 
Let boys know really what they are going to measure before 
they begin to measure. 

Some Snags 

FORCE. Do not try to define the term force. What is the 
use of saying, " Force is * that J which produces motion "? 
How are we then to define the term " that "? Suppose we say, 
" Force is the (vector) rate of change of momentum." What 
boy will understand, really understand? A boy has some sort 
of working idea of force, right from the first; he knows that 
a force is acting when a thing is being pushed or pulled about; 
later, he associates force with weight; still later, a clearer idea 
begins to dawn. But it is foolish to make the boy define the 
term. And if a ready-made definition is given him, it will 
almost certainly be open to criticism. 

When we say that force is the product of mass and accelera- 
tion, we do not define force. We may say that two forces are 
equal when they give the same acceleration to the same mass; 
or, we may say they are equal if, acting in opposite directions,, 
they are in equilibrium. But this is not a definition of force. 



MECHANICS 129 

A force applied to a body cannot be uncoupled and applied 
to another body, as an engine is uncoupled from a train and 
coupled to another. How then is it possible to say what accelera- 
tion a force applied to a first body would give to a second 
body if applied to it? The rule that the force acting on a body 
is equal to the product of its mass and acceleration depends 
on the possibility of measuring three magnitudes, the force, 
the mass, and the acceleration. But mass is not capable of 
measurement independently of the notion of the equality of 
two forces. We do not define the smell of sulphuretted hydro- 
gen as the product of the separate smells of sulphur and hydro- 
gen. The analogy is admittedly entirely irrelevant, but it is 
scarcely more illogical. Poincare rightly points out that when 
we say that force is the cause of motion, we are talking meta- 
physics. We are certainly not defining force. No boy can be 
expected to frame a satisfactory definition, and he should not 
be asked to do so. If any teacher is able to frame the definition, 
by all means let him pass it on to his class. But is he able to 
do it? 

Never accept from a boy such a statement as 

force acting _ weight 

acceleration produced g 

A " mixed ratio " boy should be handed over to the chief 
mathematical master to be put in a special pillory. 

CENTRIPETAL AND CENTRIFUGAL. To teach the meaning of 
" centripetal force ", illustrations must be used carefully: a 
ball whirled round at the end of a string will do to begin with; 
then call in illustrations from astronomy. The beginner is 
always puzzled; he says: " If there is a force, there must be 
acceleration, but in this case the velocity is constant and there 
is therefore no acceleration. " A force which continually acts 
but seems to do no work save that of causing continual change 
of direction does not seem to the boy to be on all fours with 
the forces he is already familiar with. " There may be a change 
of direction, but there is no change of speed; how then can 



130 SCIENCE TEACHING 

there be acceleration?" The boy has got into his mind a too 
limited connotation of the term acceleration, and the teacher 
must clear up his difficulty. It is best to avoid altogether the 
term " centrifugal force ". Boys are apt to think of it as a 
force acting directly outward, instead of as a tangential force. 
It is quite true that we may correctly regard the two forces (cen- 
tripetal and centrifugal) as constituting the stresses in the string, 
but the term centrifugal force is nevertheless best not used. 

ACCELERATION. The generally accepted use of this term 
must remain the use for school purposes, but Sixth Form boys 
should be warned that the term is by no means so simple as 
it is often thought to be. As Professor Hobson points out, 
" the acceleration of a body " has no logical meaning unless 
either the body be of negligible dimensions or the acceleration 
be taken to mean the acceleration of some one particular point 
in the body; for, in general, a body can move not only trans- 
lationally but also rotationally, and thus different parts of the 
body may have different accelerations. In order that Newton's 
laws may have a precise meaning, it must be assumed either 
that the bodies referred to in them are considered as masses 
concentrated at points, or as bodies which, though of definite 
size, are, at their centroids, equivalent to such concentrated 
masses, the forces between any pair of such bodies being along 
the straight line joining their centroids. This is of little or no 
consequence in ordinary school practice, but Sixth Form boys 
should be aware of it. 

CONSERVATION OF ENERGY, OF MATTER, AND OF MASS. 
Here again a warning is necessary in the Sixth Form, though 
the older notions will continue to be used in the Fifth. 

The term energy is of comparatively recent introduction 
and represents the work that may be done by forces acting on 
matter. It may be observed and measured in a multitude of 
forms. It may take the form of sound, light, heat, electric 
charge, electric current, raised weights, bent springs, moving 
and spinning bodies, and radiation generally. But it has been 



MECHANICS 131 

found that radiation strangely simulates some of the properties 
of matter. It exerts a minute pressure on bodies receiving it, 
exactly as if it possessed momentum, and it therefore looks 
as if radiation is itself a form of matter, even if only a temporary 
form. The electrical theory of matter emphasizes the shadowy 
nature of the distinction between matter and energy. It looks, 
indeed, as if matter were merely a form of energy. Thus a 
teacher must be on his guard against giving too much emphasis 
to the doctrines of the conservation of matter and energy. 

When we talk about the conservation of matter, we certainly 
do not mean that such physical properties as extension, colour, 
hardness, conductibility of heat and electricity, &c., persist 
unchanged, for they are subject to very large changes in what 
we regard as one and the same material system. What, then, 
is a boy to understand by the statement that matter can neither 
be created nor destroyed? If we assert that what persists un- 
changed is a sub-stratum, substance itself, not identifiable with 
any of the physical properties but regarded as their bearer, 
we make verification impossible, and our assertion belongs to 
the realm of metaphysics, not of science. What is a boy to 
make of it? 

We cannot infer that conservation of matter means con- 
servation of weight, for weight varies with the place where it 
is measured. But if, for different localities, we divide the weight 
by acceleration due to gravity, we obtain a measure of the mass 
of the body, and then the conservation of matter is reduced to 
the conservation of mass. And conservation of mass seems to 
imply that mass, as a measurable quantity, is unchanged in 
amount throughout all the chemical and thermal changes that 
may take place in an isolated material system. 

But our increasing knowledge of electrons is driving us to 
the conclusion that mass does not occupy the simple position 
that hitherto has been assigned to it in the mechanical theory 
referred to. In fact, we may no longer assume that mechanical 
masses of bodies are constant. Dynamical mass may no longer 
be regarded as fundamental and irreducible. The Sixth Form 
boy should know this, but he may be told frankly that, at least 



132 SCIENCE TEACHING 

for the present, all problems in physics must be solved in the 
old way, our knowledge of the intimacy of relationship between 
matter and energy being still very fragmentary. 

Units 

Although written half a centuiy ago, Dr. W. Garnett's 
Elementary Dynamics deals with the question of units in a w r ay 
that has always been regarded as exceptionally clear and com- 
plete, and every teacher of mechanics should read it. Professor 
Hicks 's book on the same subject is also excellent. And genera- 
tions of science teachers have been familiar with Everett's 
C.G.S. system of units. In short, the subject of units has 
been treated so exhaustively, so clearly, and so often, that both 
from the point of view of science and from that of teaching there 
is really no more to be said. Yet teachers do not agree as to the 
best methods of procedure or, in fact, about the units to be used. 

About certain things, however, all agree. One is that a boy 
must clearly understand what is meant by fundamental units 
and by derived units; another, that he must clearly understand 
that the measure of a quantity varies inversely as the magnitude 
of the unit; a third, that it is desirable he should be able to 
write down at once the dimensions of a derived unit, even 
though in the actual measuring of such units he does not have 
recourse to the fundamental units (for instance, in measuring 
a velocity he might take as the unit of velocity the velocity of 
sound). But whether preference should be given to weight 
or mass, or to the use of pound or poundal, teachers simply will 
not agree. 

There is much to be said for adopting, in the first place, 
a unit appropriate to the business in hand, e.g. the ton for 
coal, the pound for sugar, the ounce for pepper, the grain for 
strychnine. There are circumstances in which we might speak 
of the ton-mile-hour unit much more appropriately than the 
centimetre-gramme-second unit. 

A beginner often confuses mass and weight, and is it sur- 
prising? Try to help him to obtain a precise notion of weight 



MECHANICS 133 

as a downwardly directed force; help to clarify his notion of 
mass by reference to bulks of material with which he is familiar, 
the bulk of a pound of butter, of a two-pound loaf of bread, 
the amount of stuff quite apart from its weight. Tell him to 
imagine a person living in the moon and buying a pound of 
butter there: how would the bulk of the butter compare with 
the bulk of a pound sold on the earth. He will soon get the 
right idea of the distinction between mass and weight, even if 
he cannot express himself satisfactorily in words. And the dis- 
tinction is all important. 

Make the boy understand that the mechanical engineer uses 
the unit of weight. The mechanical engineer regards weight 
the pull of the earth as the fundamental quantity, and looks 
upon mass as a subsidiary thing. But the electrical engineer 
and the physicist regard mass as the fundamental unit, and look 
upon gravitation as something quite unimportant. The boy 
must be taught never to mix up the two ideas. Wherever in 
a problem based on gravitation m comes in, m must be replaced 
by Vf/g. But if mass is to be the fundamental unit, wherever 
in the problem W comes in, W must be replaced by mg. Numeri- 
cally the problem must have W all the way through, or m all 
the way through, the equalizing equation being W == mg. In 
earlier experiments in mechanics real weights are naturally 
used, and the beginner becomes familiar with W. From the 
first he should use this symbol in his calculations, and by the 
time he reaches the subject of gravity, and learns that W (or F) 
= mg y the W will be an old friend. It is a mistake to allow 
a boy to use m in his equations, until he has covered a good 
deal of elementary ground. 

Boys' answers to questions in mechanics are often wrong 
because of confusion of units. This is shown at once by the 
answer being a recognizable multiple or quotient of the correct 
answer, and the boy's particular blunder thus stands revealed. 
Momentum is confused with work done; g is called a force; 
and so on. 

It pays to teach units very thoroughly, whatever a teacher's 
pet scheme of units may happen to be. 



i 3 4 SCIENCE TEACHING 

CHAPTER XII 

Physics 

The Normal Course: General Considerations 

In physics, even more than in chemistry, the signs of the 
times are that teachers are no longer wedded to the traditional 
method of beginning the subject by rigorously establishing 
first principles, and finishing it by making casual references to 
applications in everyday life and by providing the boys with 
little arithmetical problems in preparation for the examination 
day. Teachers no longer fear to offend the rules of logic, and 
they no longer shrink from allowing boys to contribute know- 
ledge already acquired from other sources. 

In any branch of physics, there is much to be said for 
developing the subject from some selected topic about which 
the pupils already have a certain amount of general know- 
ledge. Suppose, for instance, that a course on heat is to 
include, as its principal feature, the study of internal- and 
external-combustion engines. Beginners might, at the outset, 
be given an insight into the working parts of an ordinary steam- 
engine (stationary or locomotive), and of a motor-cycle or 
motor-car; as much, say, as a repairing workman or a com- 
petent driver could give them. The facts gleaned and suggested 
during these (say) two first lessons would be sorted out and 
amplified in such a way that they could be grouped under 
the usual headings: expansion, colorimetry, change of state, 
and so forth; and in this fashion a course of work could be 
drawn up on almost orthodox lines. But the boys would feel 
that the course was really the outcome of their own suggestions 
made concerning things in which they would be interested all 
their lives, and not a course thrust upon them for examination 
purposes. Revision towards the end of the course would include 
another examination of the engines, but this time the examina- 



PHYSICS 135 

tion would be a scientific examination, based on much fuller 
knowledge. Boys are always impressed with the use, made by 
inventors, of ordinary scientific principles. 

Alternatively, the subject might be approached in a different 
way, the American " topic " method supplying the key idea. 
The class of beginners would be asked to give instances of 
apparatus or of machines or of phenomena in which heat 
and cold are concerned: a kitchen-range, a gas-cooker, a kettle, 
a bunsen burner, a thermos flask, a foot-warmer, a thermometer, 
a bursting boiler, the putting of a tyre on a wheel, and a score 
of other things. As before, there would be a sorting out and 
grouping of the suggestions; main principles would be estab- 
lished one by one in the usual way, a particular phenomenon 
suggested by the boys being made a thing to work from, and 
to remain the centre of interest. 

Suppose a course of light is to lead up to a knowledge of 
optical instruments. The boys might, to begin with, be supplied 
with a few instruments, say a common magnifying glass, a 
kaleidoscope, an old telescope, perhaps even an old microscope 
with a coarse objective, and told to gather what knowledge they 
could, consulting books if they liked, but warned, of course, 
about the careful handling of the instruments. They will 
glean all sorts of odds and ends of information, some correct 
and useful, some crude and worthless, and over some things 
they will be greatly puzzled. It is easy to convince them now 
that they have much to learn, and, if thought necessary, an 
ordinary traditional course of work may be imposed on them, 
to be readily accepted because of a recognition and under- 
standing of its value. In teaching light, it is particularly neces- 
sary to try to make the pupils understand the actual physical 
nature of optical phenomena. Do not be in a hurry to reduce 
the phenomena to mere geometry. The geometry must come, 
of course, but it must take a second and not a first place. 

Suppose a course of sound is to lead up to a knowledge of 
musical instruments. Begin with the examination of, say, a 
piano, and compare with a violin. The boys will learn much 
if they are encouraged to talk things over amongst themselves, 



136 SCIENCE TEACHING 

and the monochord will soon become child's play to them. 
Wind instruments are more difficult. Begin, perhaps, with a 
tin whistle, and then with some kind of free-reed instrument 
like the harmonium. The cornet and kindred instruments are 
too difficult until a later stage. And the grand organ can be 
treated only as a complicated piece of mechanism with secrets 
too difficult for any but advanced pupils to unravel, though 
the keys (with manuals and pedals), the stops, the sound 
boards, the wind-chest and valves, and the pipes, all lend 
themselves to a preliminary treatment within a fairly elemen- 
tary course. But, after all, the proper understanding of wind 
instruments will usually be made to depend on a close study 
of the laboratory pattern organ-pipe. Until this is done, 
little headway can be made by induction from facts produced 
by simple experiments on complete wind instruments. It must 
be admitted that sound is a difficult subject to teach, though 
much of the matter of the ordinary text-books is unsuitable 
and unnecessary in a school course and might, without much 
loss, be consigned to the academic dust-bin. It is doubtful 
wisdom to take up the subject in the Middle Forms, though 
Sixth Form boys ought to have clear ideas of the principle 
underlying wave-motion, interference, resonance, harmonics, 
and the measurement of the velocity of sound, if nothing more. 

Suppose a course of electricity is to lead up to a knowledge 
of electric lighting and electric traction, as undoubtedly it 
should. In such circumstances, is there any need to teach 
static electricity at all? Probably not, though some teachers 
say they can never give their pupils clear notions of potential 
unless they approach the subject through electrostatics. 

After a few preliminary lessons on the production and 
properties of an electric current, a boy may be given a first 
insight into the school or house electric lighting installation. 
He will quickly understand the supply cable and dividing box, 
the meter, the main fuse, the main switch, and get some pre- 
liminary notion of the distribution board and the wires to the 
lamps. The transformer (if any) should be considered at a 
later stage, but enough will have been done to get the boy 



PHYSICS 137 

thoroughly interested in the subject as having great practical 
value. 

Most town boys will be able to contribute something to 
the common stock of knowledge concerning special systems 
of electric lighting industrial lighting, shop-window lighting, 
street lighting, domestic lighting, the lighting of public build- 
ings, theatre lighting, train lighting, electric signs, motor-car 
headlights and anti-glare devices all applications of a single 
main principle but with engineering and mechanical differences 
that make a strong appeal to a boy. Call for such contributions 
of knowledge, sort out the facts, reduce them to the very 
few and easily understood underlying principles, and make the 
boys realize how extraordinarily useful a knowledge of elec- 
tricity is. 

There is this in common with electric lighting and traction, 
that both have the same parentage, viz. the dynamo and the 
motor; all else is accessory. Hence the teaching must be 
concentrated on these two things: the development of elec- 
trical energy and its transformation into other forms of energy. 
The course of instruction can therefore be planned out with 
that end in view. Electro-dynamics, electro-magnetics, and 
induction of currents, will be of primary importance; the 
careful consideration of electromotive force and resistance will 
therefore find an early place in the sequence of topics forming 
the syllabus of \vork; and the boys should make an early and 
close acquaintance with the various everyday working instru- 
ments of which the galvanometer is the type. 

In short, before drafting a working syllabus in any branch 
of physics, decide upon the end in view. The ordinary text- 
book sometimes tries to provide the needs of many ends at 
the same time, and the boy completes his course without clear- 
cut notions of any part of the subject as a unity. 

Present-day Developments in Electrical Courses 

[3| In any present-day course in electricity, a boy must become 
familiar with all the common electrical units the ohm, volt, 



138 SCIENCE TEACHING 

ampere, joule, watt, and kilowatt, PRACTICALLY. He must get 
to know them as he knows the foot, the metre, the prfund, the 
cubic centimetre, &c. He should become quite familiar with 
the voltage of the ordinary supply cable, and with the current 
consumed by the ordinary electric lamp. Such examples of 
transformations as the following should become mere child's 
play to him. 

1 . If a lamp which takes ampere is placed upon a current 
having a pressure difference of 100 volts, the lamp would be 
taking 100 X (~ 66 -f) watts, and this is the measure of 
the rate at which energy is being supplied to the lamp, and 
converted by it into light and heat. 

2. If a i6-c.p. lamp is traversed by a current of f ampere, 
working at 100 volts, the resistance of the lamp filament 

100 (volts) . 

~ .>... - - ' = 150 ohms, 
f (ampere) 

3. If a man raises 55 Ib. i foot every second, he does v h.p. 

4. Twenty loo-volt lamps each taking | ampere would be 
using (| X 100 X 20) watts 1000 watts i kilowatt = i^ h.p. 

5. If a man raises i Ib. 9 in. high, he does i joule of work. 

6. If he does i joule of work every second, his rate of doing 
work -- i watt = r-nr h.p. 

If these transformations are in any sense arithmetical puzzles 
to the boy, it is evident that he is not familiar enough with 
the units and their relations practically. Practical familiarity 
is essential, and the school electric supply current is probably 
the best means of giving concrete notions. Boys can easily 
be made to see why the current supplied to every house in the 
town is maintained uniformly at the same pressure (voltage), 
although the current consumed varies with the house. (The 
water supply and pressure give a useful analogy.) An interest- 
ing problem for boys to try to solve: why does a very slight 
increase in pressure cause a great increase in the amount of 
light? 

Pressure and current are constantly confused by boys. 

Visits to generating stations are of great value, especially 



PHYSICS 139 

if the sympathy of the engineer in charge can be enlisted. 
The great majority of school experiments in electricity are 
necessarily on a toy-like scale, and the boys ought to see the 
real thing. 

Electric traction forms a fitting sequel to lighting considera- 
tions. New points: the continuous connexion between the 
motor on the vehicle and the stationary dynamo, viz. by means 
of either a third rail or an overhead conductor (the old stud 
system still survives in Lincoln); the reduction of the 5000 
volts from the central station to 500 volts for distribution, 
and why; contrast the rapid acceleration of an electric train 
with the gradual acceleration of a steam-engine (the motor 
gives its maximum torque at starting); and so on. 

Telegraphy and telephony should be included in any school 
course. But although telegraphing by wire and cable lends 
itself to comparatively elementary demonstration and explana- 
tion, wireless telegraphy is a subject for older rather than for 
younger boys, except on the practical side. 

A similar remark applies to telephony. As a practical 
instrument, the telephone is easily understood, and a school 
installation may well be undertaken by the boys. But the 
theory of the telephone is rather difficult. The conversion of 
the original sound vibrations into undulating currents of elec- 
tricity, and the subsequent reproduction of the vibrations, can 
be dealt with effectively only as the sequel to a sound general 
knowledge of elementary physics. The precautions to be 
taken against the inductive effects between neighbouring wires 
is only one of several sources of puzzlement to boys. 

By all means encourage boys to interest themselves in 
" wireless ". They learn much from rigging up a " set " of 
their own. But the theoretical considerations of the subject 
cannot be taken until fairly late in the school course. And any 
attempt to teach the theory of wireless before some knowledge 
on the practical side has been acquired is not likely to prove 
successful. 

Before the close of any school course in electricity, provision 
should be made for a review of the whole subject historically. 

(E72) 11 



I 4 o SCIENCE TEACHING 

A new and interesting light is thrown upon the subject when 
boys see how the original crude notions of electricity and its 
production have been gradually transformed by successive 
investigators. Such names as Gilbert, Franklin, (Epinus, 
Cavendish, Coulomb, Poisson, Galvani, Volta, Woolaston, 
Davy, Oersted, Ampere, Ohm, Faraday, Maxwell, and Kelvin 
appear on the pages of almost every text-book, but few boys 
realize what great steps forward these men made in electrical 
science. To appreciate what each worker did, the boys must 
understand the limited state of knowledge at the time he lived. 
Unfortunately, school life is not long enough to do much in 
this direction, but boys should be encouraged to read such 
books as Faraday as a Discoverer and learn something of the 
man, of his methods, and of the world of science into which 
he was born. 

The Necessity for a Greater Width in a 
Physics Course 

The content of a school physics course is often unduly 
limited. Important parts of a subject are sacrificed to academic 
considerations of no practical value. The mathematics of 
physics occupies much too large a place, and lesson after lesson 
is devoted to mere algebra. 

" General physics " needs far more attention, as was pointed 
out in the Prime Minister's Science Committee's Report. 
And this does not refer merely to the group of subjects some- 
times summed up under the term " properties of matter " 
(capillarity, surface-tension, viscosity, &c.), but to the working 
of such things as airships, airplanes, submarines, turbines, 
where the whole thing is a complex (so to speak) of associated 
mechanical and physical principles, and will well repay careful 
analytical treatment. 

Consider such a common thing as a gramophone. As a 
practical instrument it is easy enough to understand, but its 
adequate consideration, theoretically, demands a sound elemen- 
tary knowledge of physics. An instructive visit may be paid 



PHYSICS 141 

to a gramophone factory, in order that boys may observe the 
successivS processes in the manufacture of a record the 
moulding and shaving of blanks, the taking of a record, the 
duplication of a record, the production and duplication of 
matrices, and the like: such a wonderfully simple series of 
manufacturing artifices is to the boys a revelation. The boys 
are interested, and are now keen to understand the reproducing 
machine, the gramophone itself. This machine readily reveals 
all its secrets save one, viz. that of the so-called sound-box 
and diaphragm, and at this stage the physics teacher has to 
step in. But of course the boys will not be able to understand 
the actual recording and reproduction of sound unless their 
previous physics course has included lessons on wave analysis. 
Of all subjects in physics, wave-motion probably stands first. 
In importance, it ranks perhaps even before energy. It is at 
the bottom of everything else sound, heat, light, electricity, 
magnetism. It must be taught and taught thoroughly, other- 
wise nothing will be understood properly. Even Sixth Form 
boys sometimes confuse wave-motion with the to-and-fro 
or up-and-down motion of the medium. And they do not 
always understand clearly the connexion between wave-length 
and frequency, or the way in which the velocity of a wave 
depends on the elasticity and density of the medium. Begin 
with visible water-waves. Then pass on to invisible air- waves; 
tuning-fork records may be made, and wave-length and fre- 
quency demonstrated. Let the boys see and understand that, 
e.g., the middle A on the piano (the orchestra tuning-note) has 
a frequency of 217, and since the velocity of the sound-wave 
is 1132 feet per second, the wave-length in this case must be 
5 feet 2 inches. Show clearly how we know that there are air 
waves. Then we come to aether waves. Give a short account of 
Maxwell's forecast in 1864 and Hertz's first laboratory success 
in 1887; then of the work of Lodge, Marconi, and Fleming. 
Consider first an sether wave of, say, 300 metres in length; 
since the velocity of light is 300,000,000 metres a second, the 
frequency of the wave must be 1,000,000. Thus if the wave- 
length of a wireless station is 365 metres, receivers must be 



1 42 SCIENCE TEACHING 

tuned to a frequency of 822,137. But the water-wave and the 
air-wave must come first; to a boy they seem to have a greater 
reality than an aether wave. One important point for a boy to 
understand about waves is that velocity is nearly always measur- 
able; and that if either length or frequency is then measur- 
able, the other can be calculated from the relation v -- /. 

It is well to emphasize the importance of a knowledge oj 
waves and wave-motion by giving some account of interest- 
ing applications. One such application is Constantinesco's 
transmission of power through water by means of wave impulses. 
And boys are always interested in Constantinesco's synchroniz- 
ing gear by means of which a Vickers machine gun could fire 
over 1000 bullets a minute through the rapidly revolving pro- 
peller blades of an airplane. 

We have already referred to the importance of energy as 
a main subject of physics. In schools it does not receive any- 
thing like the amount of attention it deserves, and the whole of 
physics might very well be taught as just different aspects of 
energy. It would not be inappropriate to define physics as 
the science of energy transformations. 

Can a Sixth Form boy give an exact explanation of the 
action of the various toys he used when a child, or of the 
familiar phenomena and things of everyday life a spinning- 
top, a Cartesian diver, a fountain-pen, the tears on a wine-glass, 
the geometrical form of snow-crystals, a bubble of froth, the 
special qualities of a cricket ball, and a hundred others? If not, 
can it be said that his knowledge of physics is satisfactory? 

Practical Physics 

There are now so many excellent books on practical physics 
published that the difficulty is to make the best choice. Even 
some of the older ones should still find a place on every teacher's 
shelves, e.g. Glazebrook and Shaw's and Stewart and Gee's. 
The older books often give invaluable hints on manipulation, 
hints that are apt to be crowded out from a newer book. But 
some of the older books must be used with circumspection. 



PHYSICS 143 

They contain descriptions of experiments that are no longer 
worth including in a school course; on the other hand many 
experiments which now ought to be included naturally find no 
place in such books. The books were written at a time when, 
e.g., current was not available for laboratory experiments, and 
such experiments as were suggested were sometimes very 
remote from practical life, and not infrequently they failed to 
demonstrate or to verify adequately the principle for which 
they were specially devised. 

An important point sometimes overlooked in practical work 
is the necessity for comparing different types of instruments 
all having a common ancestry. Consider, for instance, the 
number of electrical instruments consisting, essentially, of a 
coil and a needle? Why the differences in pattern, why the 
differences in the needles and in the coils? The differences 
are the key, as differences always are in methods of scientific 
investigation. It is not enough to tell a boy about the differences 
between different types of galvanometers, ammeters, volt- 
meters, &c. He must examine the coils and examine the 
needles, and see the differences for himself. 

More Snags 

THE THEORY OF HEARING. Is it of any use to spend time 
in trying to make Sixth Form boys understand Helmholtz's 
resonance theory of hearing? Probably not, since the theory 
can no longer be upheld. An outline of the theory might be 
given, and then reasons for its rejection. It is to be regretted 
that many physiology text-books continue to compare the fibres 
of the basilar membrane with piano strings. A continuous, 
very small, spread-out membrane, varying in width from the 
base upwards in the proportion of about i to 10, is supposed 
to contain a series of end organs which must number at least 
2000, each being delicately attuned to vibrate in sympathy with 
one periodic vibration only; and this marvellous collection 
of resonators must be fully developed at birth! Helmholtz 
first thought that the external pillars of the organs of Corti 



i 4 4 SCIENCE TEACHING 

were the resonators, but when it was shown that these do not 
exist in birds, which have particularly acute hearing, he aban- 
doned the external pillars in favour of the fibres of the basilar 
membrane. Nearly every other structure of the cochlea has 
at one time or another been credited with the function of a 
resonator. 

It is a matter of observation that the broad fibres of the 
basilar membrane are all imbedded in a membrane and are 
forced to move together with no chance of vibrating singly; 
also that the membrane is in liquid, with no power to move 
against it. How can such delicate fibres with no chance of being 
tuned under tension, be compared to piano strings? What is 
the use of illustrating Helmholtz's theory by experimenting 
with hard materials like brass resonators or steel wires, and 
using as the exciting vibrations the vibrations of tuning-forks 
maintained at constant pitch? 

The basilar membrane and its fibres are probably non- 
elastic tissues, and are therefore non-vibrating bodies which 
have no resonance periods of their own. Moreover the mem- 
brane being in a liquid must follow the movements of that 
liquid exactly. 

It is doubtful if any theory of hearing will be satisfactory 
unless it begins with the assumption that the cochlea as a 
whole responds to sound vibrations. Any analysis of the 
auditory sensations that occur is probably made in the brain 
and not in the cochlea. It is possible that each sound-picture 
creates a pattern and makes a composite impression in the 
cochlea, but it is improbable that the cochlea is an analysis 
apparatus. 

It will be enough to tell the boys that we do not know how 
we hear, that no theory so far put forward is satisfactory, that 
even a great man like Helmholtz was probably mistaken by 
appearances, the radiating fibres suggesting to him a musical 
instrument. 

THE REFRACTION OF LIGHT. Approach this subject by 
first giving instances of retarded velocity: a toy trolley running 



PHYSICS 145 

down a sloping table, the upper half of which is smooth, the 
lower half covered with baize; a line of soldiers marching on 
their front over a field, the first part of which has just been 
mown, the second part being still long grass: if in either case 
the approach be normal to the line of separation, there is 
merely retarded velocity; if oblique to the line of separation, 
the front slews round as well (see Mr. W. E. Cross's book). 
Show that this slewing round is inevitable and is general] 
that therefore it applies to light as to everything else. Let the 
boy realize from the first that the " bending " of a " ray " 
is merely due to retardation, in a denser medium, of the whole 
wave-front. It is asking for future trouble if the sine law 
is worked out first, and the velocity- ratio is mentioned later 
as a sort of trivial consequence of this law (and this is often 
done!). 

Show clearly that total refraction never occurs: there is 
always some reflection. And show that refraction into a rarer 
medium cannot take place unless the angle of incidence is 
less than a critical angle (again illustrate with the marching line 
of soldiers). 

COLOUR VISION. -I have never yet discovered a Sixth Form 
boy who could give an intelligible account of colour vision; 
and I am inclined to think that the difficulties underlying rival 
hypotheses are greater than can be properly dealt with in 
ordinary school practice. The Young-Helmholtz-Maxwell tri- 
chromatic hypothesis is the best hypothesis covering all the 
facts known at the time of its enunciation, and Helmholtz 
himself stated clearly that the hypothesis was only an hypothesis 
and did not claim to be fact. Even down to the present time 
it has not been found possible to demonstrate the existence of 
three different kinds of nerve elements corresponding to the 
three fundamental colour sensations. The theory is loaded 
with subsidiary hypotheses, many of them quite inconsistent 
with one another. Still, Professor Peddie's book on Colour 
Vision is an uncompromising acceptance of the theory as a fact, 
though it does not answer the main objections to the theory. 



146 SCIENCE TEACHING 

The rival hypothesis of Herring assumes retinal chemical 
changes under the influence of light, and it also assumes that 
white is an independent sensation, and not the secondary 
result of a mixture of primary sensations. But here again the 
difficulties in the way of acceptance of the hypothesis seem to 
be insuperable. 

Dr. L. C. Martin's book on Colour and Methods of Colour 
Reproduction gives an admirable and unprejudiced account of 
the facts and views of different authorities. Professor E. H. 
Barton puts forward an interesting hypothesis of syntony 
(sympathetic vibratory response) which seems to explain the 
chief facts of vision. Helmholtz's Physiological Optics will 
always remain a classic, even if his hypothesis is finally super- 
seded. Professor Michael Foster's Physiology, although written 
as far back as 1891, still gives (in Part IV) the best summary 
of the whole subject, and selections might well be mastered 
by Sixth Form boys. 

THE RIVAL HYPOTHESES OF LIGHT. Although the principles 
of these two hypotheses differ widely (the Newton corpuscular 
hypothesis and the Huygens-Young-Fresnel-Clerk Maxwell 
undulatory hypothesis), there is no doubt that both hypotheses 
were in some w r ay interwoven in Newton's mind. " Do not 
all fix'd Bodies, when heated beyond a certain degree, emit 
Light and Shine; and is not this Emission perform'd by the 
vibrating motions of their parts?'' And in Query XVII he again 
compares the ray of light falling on the surface of some substance 
to a stone thrown into stagnant water. Still, Newton does not 
seem to have thought, as Huygens did, of the ray itself as just 
a travelling wave. 

The two hypotheses are well within the understanding of 
Sixth Form boys, who do, however, sometimes find difficulty 
in visualizing an electromagnetic wave. And boys are always 
interested in learning how, when about a century ago the 
velocity of light in water was measured, and the velocity-ratio 
in the two media, air and water, therefore became known, the 
corpuscular hypothesis had to give way to its rival. 



PHYSICS 147 

On ttye basis of the electromagnetic hypothesis a develop- 
ment of the earlier wave hypothesis a beam of light is recog- 
nized as having a certain momentum. Moreover, radioactivity 
seems to show that the process of radiation as a whole depends 
in part on the movement of electrons. In the X-ray bulb, for 
instance, a stream of electrons, which is truly a corpuscular 
radiation, strikes a block of metal in the centre of the tube. 
Energy of radiation is carried outwards through the walls of 
the tube in the form of X-rays, that is to say of wave motions 
in the aether. When they strike matter, such as the film of a 
photographic plate, the wave radiation seems to disappear and 
to be replaced by moving electrons which produce all the well- 
known effects ascribed to X-rays. It seems probable that this 
mutual play of waves and electrons is carried through the 
whole realm of radiation. But we do not know how the energy 
of the electron in the X-ray bulb is transferred by a wave- 
motion to an electron in the photographic plate. 

Clearly the phenomena of photo-electricity calls for a revival 
of the corpuscular hypothesis in some form, and relativity is 
making the same clamant demand. On the other hand, the 
well-established phenomena of interference cannot be made to 
square with any form of corpuscular hypothesis. 

The problem is to reconcile the two hypotheses. Professor 
Lorentz's Royal Institution lecture on " The Radiation of 
Light ", given on ist June, 1923, and Sir J. J. Thomson's 
Fison Memorial lecture on " The Structure of Light ", given 
in 1925, give indications of a possible means of reconciliation: 
we probably have to accept both the waves and the corpuscles. 
But the evidence is rather outside the range of Sixth Form 
work. 

THEORIES OF MAGNETISM. Boys can understand the theories 
of last century, those developed by Poisson, Ampere, Weber, 
Maxwell, Ewing, and Curie. But since the beginning of the 
present century, when attempts were made by Voigt and J. J. 
Thomson to outline an electron theory of magnetism, based 
on the magnetic effects of a moving electron, theoretical develop- 



148 SCIENCE TEACHING 

ments have become rather too difficult for inclusion in a school 
course. Boys cannot appreciate the objective side of the evidence 
on which the theories of Langevin and Weiss are based. And 
Honda's later theory of gyroscopic motion of the molecule, 
to account for diamagnetism and paramagnetism, is decidedly 
obscure; and after all, more recent evidence suggests that the 
gyroscopic motions do not arise from molecular rotations but 
from a gyroscopic property of the electron itself. It is pro- 
bably enough to tell a boy that recent evidence suggests that 
the ultimate magnetic particle is neither the molecule nor the 
atom but the electron itself, the electron being not merely an 
electric charge but a magnetic doublet (magneton). At the 
present moment, magnetic theory is too obscure, and the 
experimental evidence on which it is based is too fragmentary, 
to make its inclusion in a Sixth Form course advisable. Time 
can better be devoted to something else. 

THE ^ETHER. Beware of befogging a boy's mind by telling 
him that the hypothesis of an all-pervading aether has been 
given up. After all, the aether has an honest British ancestry 
Newton, Kelvin, Clerk Maxwell, Faraday, Lodge, Larmor. 
Is it possible to deny that a substratum of some kind exists? 
Light-waves and an electric field seem to demand the displace- 
ment of the small parts of something, a displacement involving 
strain with its energy of elastic deformation. When some of 
our foreign friends and their English disciples describe this 
as the displacement of varying " space ", they seem to mean 
something very different from the empty " space " which the 
term space commonly suggests to us. Fundamental space is, 
presumably, uniform, the same everywhere. As soon as the 
qualities of space are made to depend on the presence of 
adjacent portions of matter, it ceases to be pure space and 
becomes an interconnecting medium with physical properties. 
We may as well continue to use the term " aether " as change 
it to " manifold "; even if we think in terms of relativity, and 
think of space-time instead of space and time separately, the 
consequential " four-fold extension " still possesses properties, 



PHYSICS 



149 



and is clearly something quite different from empty " space ". 
Few school boys will be able to understand the relativity 
conception of gravitation, and the properties of " space-time " 
will therefore rarely be a topic for inclusion in a school course. 
But all boys will require to know something of the all-pervading 
wave-carrying medium, and the term aether is, for this purpose, 
to be preferred. 

Science teachers are not infrequently asked by boys why 
wireless rays " bend round the earth ". This is a question 
which concerns the high-level atmosphere, as well as the 
aether. Reference may be made to Sir Joseph Larmor's paper 
read in Oct., 1924, to the Cambridge Philosophical Society, 
and Professor Fleming's article in Nature, 24th Jan., 1925. 

CARNOT'S CYCLE AND ITS APPLICATIONS. Teachers invari- 
ably find this a difficult subject to expound, and, even at the 
end of their physics course, Sixth Form boys often reveal a 
very hazy knowledge of parts of the subject; and the reason 
usually is that they have a too slight practical acquaintance 
with the steam-engine, and have been introduced to the mathe- 
matical treatment of the subject before they really knew the 
inner physical significance of it. 

The following sequence of teaching stages has been found 
to answer well. 

1. It is assumed that the usual elementary course of heat 
has been done, including change of state, the kinetic theory of 
gases, heat and work relations, the heat engine, the mechanical 
equivalent, efficiency of an engine. Revise if necessary. 

2. More advanced work may now be taken in hand, e.g. 
heat and work: an outline of the researches of Rumford, Davy, 
Joule. First Law of Thermodynamics: W = JH. 

3. The Steam-engine: a machine for changing the heat of 
fuel into work. Watt's main improvements on Newcomen's 
engine: condenser, double-action, expansive working, indi- 
cator, slide-valve and eccentric, parallel motion, reversing gear, 
governor, fly-wheel, crank and connecting-rod. The boys must 



150 SCIENCE TEACHING 

be given the opportunity of examining a station^ r y steam- 
engine in motion, in order that they may obtain a clear under- 
standing of the practical working of the various parts. Nearly 
every feature of the modern reciprocating engine is to be found 
in Watt's later designs. Until the boys understand the general 
action of an engine, further work is likely to be artificial. In 
particular, let them learn all they can about the cylinder and 
condenser, the indicator, and the " working substance ". 

4. Indicator and Indicator Diagram. If at all possible, let 
the boys see an indicator in action.* Disconnect it from the 
cylinder, and show how the connecting gear of the engine turns 
the barrel of the indicator and how the pencil then draws the 
horizontal atmospheric line; then disconnect the gear, but 
connect up with the cylinder, and show how the pencil draws 
the vertical line. Now ask the boys what sort of a line will 
be drawn if both connexions are made. Realizing they are 
dealing with pressure and volume, they will probably think of 
a Boyle's law curve, or at least some form of line. Now let 
them see the diagram actually drawn, and then ask the working 
engineer to explain, in his own non-technical language, the 
significance of the diagram. (It is much better that the engi- 
neer's explanation should come before the teacher's.) The 
engineer will explain that the pressure on the cylinder is con- 
stantly varying, and that this varying pressure is translated by 
the indicator to the eye; the cylinder of the indicator and the 
cylinder of the engine being in communication, the indicator 
responds exactly to fluctuations of pressure in the engine 
cylinder. He will also explain how the diagram shows the 
variation of the steam at every point of the stroke, the cushion - 

* Otherwise they will almost certainly fail to realize the full significance of the 
diagram. Arrangements may usually be made for boys to see an indicator working 
in the mechanical laboratory of a technical college, where engines are provided for 
purely instructional purposes. If a teacher can make friends with the works 
manager of a big local engineering firm, and obtain permission for the boys to be 
present on the test-bed when an engine is being put through its acceptance tests, or 
when some defect in the working of an engine is being investigated, light will come 
to the boys as it can come in no other way. 

In any case, instruction must be given in the actual methods of recording pressure 
variations. If nothing but diagrams is available for this purpose, the boys are not 
likely to understand completely. Still, well-designed and remarkably clear diagrams 
are now obtainable. 



PHYSICS 151 

ing, the condition of the slides, whether they are leaky or 
properly ^et, whether there is too much or too little lap or 
lead, whether the ports are closed and opened at the proper 
time. The indicator tells all the faults of the engine, by which 
its power is impaired. How the indicator has been improved 
since Watt's time. 

At this stage the teacher should explain how the co-ordinates 
of each point in the plane of the figure correspond to a definite 
pressure and volume. 

5. The working substance and its cycle of operations. 

6. Theory of the Steam- engine: first notions. Carnot in 
1824; Joule in 1843; then Clausius, Rankin, Thomson (Kelvin). 
Efficiency ratio. 

7. Internal energy of a given mass of gas. Joule's law. 

8. Isothermals and Adiabatics. Clear distinction essential. 
What they show in the indicator diagram. The significance of 
the greater angle of adiabatics than of isothermals to the 
horizontal, at the points where the two cross. 

9. General Equation of a Perfect Gas: pv = RT. 

10. Carnot' s Cycle and the Second Law of Thermodynamics. 
Carnot's ideal reversible engine is imaginary, and impossible 
to construct. Clear views of the dynamical theory of heat may, 
however, be obtained from it. The four operations form a 
cycle, and in them the substance is brought back to the same 
state as at first. The cycle is geometrically represented by a 
four-sided figure, bounded on two opposite sides by isothermals 
and on the other two opposite sides by adiabatics. The con- 
ditions are simple: a " perfect " gas is supposed to go through 
the cycle of changes, alternately isothermal and adiabatic. 

But these conditions never exist in practice. We must 
therefore consider Carnot's cycle with ordinary steam for the 
working substance, the engine itself still being considered ideaL 

We cannot, however, complete the cycle as Carnot's cycle 
was completed. The existence of a separate condenser makes 
the fourth stage, that of adiabatic compression, impracticable,, 
though, actually, we do stop the exhaust before the return 
stroke is complete. 



i S 2 SCIENCE TEACHING 

ii. Comparative Study of the Four Indicator Diagrams. 

* 

(i) Carnot's engine, perfect gas. 

(ii) Carnot's engine, ordinary steam. 

(iii) Ideal diagram, for steam working expansively. 

(iv) Actual diagram, showing behaviour of steam in ordinary 
cylinder. (The successive pressures represent boiler (m), atmospheric 
(ri) y condenser (/>), and vacuum (q).) 





Vols. 
(i) 




(iv) 



Why, in practice, the diagram has rounded corners as in (iv). 
The general effects of wire-drawing, and how shown in the 
diagram. Clearance and cushioning, and their significance. 
If the hypothetical engine is clearly understood, the theory of 
the real engine becomes simple. Do not forget that the influence 
of the cylinder wall and piston makes a marked difference in 
the action of the real engine as compared with the Carnot engine, 
in that they are not non-conductors. 

12. The remaining stages need give little trouble: (i) 
absolute scale of temperature; (2) entropy; (3) formal mathe- 
matical considerations. 



PHYSICS 153 

The laws of thermodynamics should not be taught as if 
they were 'finally settled dogmas. They must still be regarded 
as hypotheses only. Carnot's ideal heat-engine has been sharply 
criticized, and Dr. J. S. Haldane is critical of the cycle. 

A very suggestive book for teachers to read is Applied Heat 
by Oelschlager and Moss. It deals with heat energy from the 
standpoint of the practical engineer.* 

Tendencies of Modern Physics: Should schools 
ignore them? 

It is evident that modern physics is becoming more and 
more electromagnetic, discontinuous, and statistical. These 
things are disconcerting to those who grew accustomed to the 
great classical conceptions of the second half of the nine- 
teenth century; and now the principle of Relativity, which 
has certainly come to stay, is more disconcerting still. It is 
true that the formulae of Relativity tend to simplify the dynamics 
of very great velocities and to give a greater unity to physics 
as a whole, but the introduction of discontinuity into physics 
the theory of quanta, for instance has complicated greatly 
the explanation of phenomena apparently of the most simple 
character. Kinetic theories which have been introduced seem 
to compel us to conceive physico-chemical laws as statistical, 
from the acceptance of which some minds rebel. 

The progress of physics towards electromagnetism is 
striking. The electromagnetic theory of light unites into a 
systematized whole the phenomena of both light and electro- 
magnetism. But the tendency to explain physical phenomena 
by the laws of electromagnetism has now attacked even me- 
chanics, which seemed to be the rock foundation of the old 
physics. Inertia, the fundamental postulate of mechanics, is 
now explained in terms of the properties of the electromagnetic 
field; and Rutherford's work seems to leave us no option. 

* When the pupil not only clearly apprehends the point that, the second law 
being granted, the properties of the actual working substance cut no figure at all, 
but also fully realizes the significance of this, then and not till then is he beginning 
to know something about Carnot's theorem. 



154 SCIENCE TEACHING 

The material atom itself appears to be constituted entirely by 
charges of electricity, and all physical forces, gravitation alone 
excepted, seem ultimately reducible to electric and magnetic 
forces. Of the older physics, only the aether seems to survive,, 
though merely as a phantom of its former self. Even the two 
great principles which hitherto have governed all physical 
phenomena, the principle of the conservation of mass and 
that of the conservation of energy, are melting into one. 

Of course it is all a question of one hypothesis superseding 
another, in the light of new facts. During the last 2000 years, 
science has had many birthdays, birthdays, not mere anniver- 
saries, and on each occasion it has decked itself out in new 
raiment. 

At the demonstration table, it is best to be a little conser- 
vative over these things. After all, the " tendencies ", and the 
new hypotheses, are still in a state of flux. Certainly Form V 
should be kept within the older boundaries, if only because 
the newer physics is too difficult for them, save that, in such 
theory of electricity as is thought to be necessary, the electron 
will necessarily play an important part. Form VI, on the 
other hand, ought to know, at least in their second year, some- 
thing of the work that our great physicists are now doing. 

A Lesson on X-rays 

Here are a few notes made during the course of a particularly 
effective lesson given to a class of Sixth Form science boys. 
The teacher's Rontgen tube and fluorescent screen (the former 
was of the regulating type, but not water-cooled) cost only a 
few pounds, but was quite good enough for demonstration 
purposes. A school not thus equipped can usually get a local 
radiologist to give a demonstration. 

i. The spectrum, visible and invisible, and its 70 octaves 
of electromagnetic waves, from wireless waves of many miles 
in length to y-rays of about io~ 10 inches. Why " octaves "; 
their recognition. 



PHYSICS 155 

2. Diagrammatic view of the spectrum, with the position 
of the 13 (about) X-ray octaves, ranging from 5 x io~ 6 to 
5 x io~ 10 cm. 

3. How X-rays are produced. The Rontgen tube: its 
special features. Story of the discovery. Radiograms and their 
interpretation. Dangers of X-rays; prevention. 

4. Of the 13 octaves of X-rays, 10 are extremely absorbable; 
the remaining 3 possess remarkable powers of penetrating 
matter, and it was this that made Rontgen 's discovery 30 years 
ago so remarkable. Including the y-rays of radium, we have 
nearly 6 octaves of radiation with which the science of medical 
and technical radiology does its work. 

5. The phenomena turned to account in the industries and 
art: (i) the differential absorption of X-rays by matter of 
different densities; (2) the diffraction of X-rays. 

6. Invention of the Coolidge tube and the utilization of high 
voltages for the more opaque materials (up to 200,000 volts). 

7. Uses of radiography in industry: detection of blow- 
holes in castings, examination of steel welds, the soundness of 
steel balls intended for ball bearings, the centrality of the cores 
of golf balls, the test of the fit of a new shoe, the testing of 
aircraft materials (especially aluminium and timber), the in- 
terior detail of opal glass electric lamps, the detection of the 
forgery of valuable pictures and antiques. 

8. Medical radiology: how fractures and growths are 
located; examination of the alimentary canal (bismuth), and 
tracing the progress of digestion. How it has been shown 
from radiograms of mummies that such diseases as rickets, 
tumours, and pyorrhoea existed in ancient times. 

9. X-ray diffraction. Laue's discovery in 1912. Crystal 
analysis and structure of atoms. The simplicity of X-ray 
spectra compared with optical spectra. How X-ray absorption 
spectra and emission spectra may be obtained. 

10. The Bragg spectrometer. 



(E72) 12 



156 SCIENCE TEACHING 

CHAPTER XIII 

Chemistry 

In Close Touch with the World Around 

The school chemistry text-books of the eighties and nineties 
were much alike: a strictly formal treatment was customary from 
the beginning; the elements and their compounds were studied 
systematically; and fragments of theory were introduced, more 
or less relevantly, during the course. Then teachers began 
to flirt with the heuristic maiden; the work attempted became 
much more logical; reasoning improved greatly. But very 
little ground was covered, the theory attempted was of the 
slenderest, there was too much toying with the history of 
chemistry, and the work done was primarily a training in 
method and only secondarily a training in chemistry. In recent 
years there has been another break away, and some of the 
newer books are not only models of logical development but 
they make modern chemistry a really live subject. It is useful 
to read through Roscoe's book, typical of the older kind; then 
Shenstone's, one of the first to stress quantitative work; then 
Alexander Smith's, one of the best for the step-to-step develop- 
ment of chemical theory from the practical work actually done; 
then Mr. Holmyard's, with its attractive and in some ways 
rather revolutionary sequence; then Messrs. Dootson and 
Berry's, with its refreshingly new method of approach. These 
books are but samples, of course, but they serve to indicate 
changes made and changes pending. 

Such books as Mr. Holmyard's and Alexander Smith's make 
one important thing particularly clear, and that is that chemical 
theory is just an appropriate setting for a multitude of facts. 
And whatever method of teaching chemistry is adopted, the 
learner must be able to see clearly how every fact and every 
bit of theory fits into the completed picture. 



CHEMISTRY 157 

But Although a teacher will always have this picture in 
mind, and will always plan out his course in such a way as to 
lead to the establishing, on an experimental basis, of the main 
principles of chemistry, his selection of material may quite 
well be given a bias of some kind. A great local industry 
is almost bound to give colour to the course. Why should 
Sheffield do the same work as Stoke-on-Trent, Luton the same 
as Port Sunlight? 

Perhaps the teacher is interested in, and has special know- 
ledge of, some particular branch of chemistry. If so, why 
should he not use that special knowledge, provided that he 
keeps it within bounds? It may be that he has taken up such 
a subject as water purification, and water for industrial use; 
in that case his ordinary lessons on the physical and chemical 
properties of water might be extended specially for a week 
or so, and include the consideration of large-scale filtration, 
aeration, sterilization, and distillation, as well as such topics 
as sources of impurities, corrosion, &c. Or, he may have done 
special work, perhaps research, on the fixation of nitrogen, 
or on explosives, or on the liquefaction of gases and the manu- 
facture of liquid air, or on alloys and the metallurgy of iron 
and steel, or on silica and glass, or on alumina and porcelain, 
or on illuminants, or on food adulteration, or on the manu- 
facture of artificial silk, or on one of a score of other things. 
Why should he not make this special knowledge a radiating 
centre for some of his teaching? But it must be kept in a 
proper perspective. The danger of such special knowledge is 
that it gets out of hand; the advantage is that it is knowledge 
which the teacher has really mastered and is therefore alive. 

However the course is mapped out, every opportunity should 
be taken to illuminate and illustrate principles from the facts 
of everyday life. A lesson on sulphur would hardly be complete 
without reference to vulcanized rubber, black gunpowder, 
fruit-tree spray, and the laxative sulphates; or on phosphorus, 
without reference to matches, the sodium salt of phosphoric 
acid used in medicine, and superphosphates used in agriculture; 
or on arsenic, without reference to insecticides; or on mercury, 



158 SCIENCE TEACHING 

without reference to the two chlorides the poisonous dis- 
infectant and the purgative. And so generally. And every 
course of chemistry should include something more than pass- 
ing reference to the triumphs of recent chemical research 
artificial silk, stainless steel, chemically tanned leather, syn- 
thetic dyes, synthetic petrol, synthetic rubber, synthetic cam- 
phor (and the manufacture of celluloid), &c. 

Organic Chemistry 

The old and rather artificial dividing line between inorganic 
and organic chemistry is tending to fade away, and a certain 
amount of work from the latter branch of the subject is now 
being included in most quite elementary courses. Whether 
organic chemistry can be profitably taken up as a substantive 
branch of a two years' course in chemistry for the Sixth Form 
is a question about which teachers are not in agreement. It 
is agreed that enough ought to be done to throw light upon 
the constitution of some of the more complex molecules, and 
to make possible an intelligent understanding of our great 
industrial processes. But it is a matter of great doubt whether 
the greater part of the academic development of organic 
chemistry, as given in the ordinary text-books, is really worth 
doing in schools. Its educational possibilities are very limited, 
and as mere knowledge it is knowledge only for the elect. 

Not the least important thing for a boy to understand is 
that although an organic molecule may be large and very com- 
plex, an organic reaction usually involves only a small part of 
the molecule, and attention must be directed to that small part; 
also that the reactive part of the molecule is a characteristic 
group, and that it is on the basis of such groups that organic 
compounds are classified. Probably it is enough to develop 
ideas of such classification only to this extent: (i) deal briefly 
with the two great classes of organic compounds, viz. the 
aliphatic compounds in which the carbon atoms are linked 
together as open chains, and the aromatic compounds in which 
the carbon atoms are linked together as closed rings; and 



CHEMISTRY 159 

(2) demonstrate clearly the principles of subdivision into 
hydrocarbons, alcohols, aldehydes, ketones, acids, ethers, esters, 
and amines. If the subject is taken far enough formally to 
illustrate the main characteristics of these groups, formal work 
may then well give place to topics of a more interesting char- 
acter. But some attention must be given to carbohydrates, 
if only because plant photosynthesis requires it. It is, however, 
doubtful wisdom to devote time to proteins and fats; so far 
as those things can profitably be taken, they are best made 
part of a physiology course, when digestion, metabolism, vita- 
mins, and dietary requirements are taken up. 

Whatever form is given to the introductory course in organic 
chemistry, it may usefully lead up to elementary considerations 
of such industrial processes as the following: 

1. Coal-tar Products. The following facts ought to be 
known, (a) i ton of bituminous coal distilled at 1100 yields 
about n,ooo c. ft. of gas, i cwt. of coal-tar, 13 or 14 cwt. of 
coke, 3 or 4 gall, of light oil, and 4 or 5 Ib. of NH 3 gas (as a 
liquor), (b) The coal tar itself yields, at successive distillation: 

(i) At 170, light oil (from which is derived benzene, 
naphtha, carbolic acid, toluene, &c.). 

(ii) At 210, middle oil (derivatives = aspirin, phena- 
cetin, lysol, dyes, &c.). 

(iii) At 240, heavy oil (creosote, &c.). 

(iv) At 270, green oil (anthracene, &c.). 

(v) Pitch (for roofings, waterproofings, coatings, &c.). 

A sort of genealogical tree, more complete than this summary, 
is worth constructing and putting on the lecture-room wall. 
A certain amount of illustrative demonstration-table work is 
easily possible and desirable. So also is a little laboratory 
work. 

2. Laundering. This subject makes a strong appeal to 
girls. (The theory of washing assumes that all dirt adheres 
to fabrics because of a film of fatty substance, and that only 
when the latter is removed is it possible for the dirt particles 



160 SCIENCE TEACHING 

to be removed and carried away by the suds. Opinions differ 
as to how the film is destroyed. Beware of dogma here.) 

3. Perfumes, Flavourings, &c. An interesting classification 
of the origins of fragrances and essential oils may be made: 
from, flowers (carnation, lavender, rose, violet); from leaves and 
stems (geranium, verbena, peppermint); from bark (cinnamon); 
from wood (camphor, cedar, sandal); from rhizomes (ginger, 
orris); from fruit (lemon, lime, orange); from seeds and berries 
(almond, clove, nutmeg). Boys are surprised to learn that 
ancient and modern processes of distillation differ but little. 
Steam distillation on a small scale (steam passed through a 
mass of finely divided flowers, herbs, &c.) is easily possible for 
demonstration purposes. 

4. Rubber and Related Gums. Crude rubber. Physical and 
chemical properties. Methods of coagulation, washing, drying, 
milling, &c. Vulcanization. Synthetic rubber. Botany and 
geography: main facts. 

5. Dyestuffs and their Applications. Textile colouring and 
printing. Dyeing, staining, fixing. Mordants. Classification 
of dyestuffs. 

6. Cellulose Industries . Raw materials, properties. Solvents: 
reactions. Derivatives: mercerized fibre, vegetable parchment, 
artificial silk, lamp filaments, bronzing solutions, enamels, 
photographic films, celluloid or xylonite and its many uses. 
Explosives. 

7. Evaporated Foods and Condensed Foods. Dehydration 
and dehydrators. Theory of air drying. Vacuum drying. 
Preparation of foods. Scope of the industry: milk, eggs, 
vegetable, fish. 

If industrial processes, inorganic or organic, are to be dealt 
with effectively, a lesson or two must be devoted to such large- 
scale general operations as grinding and crushing; rolls and 
mills; grading, sifting, and screening; sedimentation and 
filtration; centrifugal machines, vacuum dryers, lixiviation, 
crystallization, calcination, reverberatory furnaces, and kilns; 
evaporation and distillation; conveyance of solids, liquids, and 



CHEMISTRY 161 

gases; elevating liquids; refrigeration; the hydraulic press. 
These processes and the machinery used are common to many 
industries and are easily explained or illustrated. But do not 
spend much time either on these things or on teaching the 
details of the large-scale manufacture of the common acids 
and of chlorine and its allied products. A few minutes at the 
end of a lesson would suffice to outline a manufacturing process, 
illustrated if possible by pictures and sectional diagrams. The 
details of such processes are of little permanent interest or 
value. 

Undue digression is always a source of possible danger. 
The work in hand must have a definite aim. Facts must be 
linked together and principles worked out. A thousand interest- 
ing facts may be given to a class, all more or less related to 
chemistry, but only very slightly related to one another. The 
facts may be useful knowledge, but such teaching must not be 
called either science teaching or science teaching. 

Practical Work in Organic and Physical Chemistry 

Whether much time can wisely be given by boys to laboratory 
work in organic chemistry is open to some doubt. Some of 
the time might perhaps be more profitably spent in getting 
the boys interested in what research chemists are doing. Organic 
chemists have not confined themselves to reconstructing natural 
substances. They have built up hundreds of thousands of com- 
pounds * not found in nature. At the present time there are 
numerous developments in the direction of producing sub- 
stances needed for particular purposes: it may be required to 
change the colour, odour, or boiling-point of a substance, and 
yet to retain its other qualities; to produce an anaesthetic, or 
other drug, avoiding some of the disadvantages of the substance 
already in use. How chemists set to work to do these things 
is always of great interest to boys. 

It is of little purpose to let boys spend much time over 

* See Beilstein's Handbuch. While many of these substances have obtained for 
their discoverers the Ph.D. degree, they are never likely to serve any other purpose! 



1 62 SCIENCE TEACHING 

organic preparations, though occasionally I have seen excellent 
work of this sort done; e.g. the preparation of ethyl acetate, 
methyl oxalate, and chloroform, from following the instructions 
in some such book as Dr. Cohen's. But, as a rule, both time 
and materials are sadly wasted over such work. One or two 
easy " estimation " exercises, say of C, of H, and of N, are of 
much greater value, but perhaps the practical work of greatest 
value is the determination of molecular weights: vapour- 
density method, freezing-point method, and boiling-point 
method. Suggestive laboratory exercises of a varied and valu- 
able kind are, however, to be found in Dr. Dunstan's little 
book, a book which makes a preliminary and fairly detailed 
study of alcohol the jumping-off ground for teaching elemen- 
tary organic chemistry. 

It is probably on the side of physical chemistry that the 
most valuable form of practical work for advanced boys may 
be found. Vapour-density determinations (Victor Meyer's, 
Dumas 's, and Hofmann's methods) require a good deal of 
manipulative skill, and they teach much. Mr. Holmyard's 
instructions for carrying out these experiments are admirable. 
In fact, his selection of experiments in physical chemistry is 
particularly good. No course of physical chemistry is complete 
if it does not include considerations of the causes of the begin- 
ning of a reaction, chemical equilibrium and reversible reactions, 
solutions and osmotic phenomena, and electrolytic dissociation. 
It is, however, true that the necessary experiments will often be 
the business of the teacher at the demonstration table rather 
than of the boys in the laboratory. An experiment performed 
must have a purpose, perhaps the elucidation of a principle. 
An experiment beyond a boy's skill is bound to fail in such 
purpose. (Mr. W. H. Barrett's book is full of useful sug- 
gestions for experimental work.) 

Occasional Re -grouping of Topics 

Suppose it is decided to make combustion the general subject 
of a term's work for an Upper Form, and that the following 



CHEMISTRY 163 

topics be jotted down to be included: flame and different types 
of gas-burners, the manufacture of coal-gas, explosions In coal- 
mines, low-temperature carbonization, fractional distillation of 
crude petroleum, acetylene, signal fires at sea, glazing and 
vitrification, self-ignition of haystacks, and of coal on board 
ship, and iron smelting. Is it worth while to detach these 
topics from the more general subjects in which they are nor- 
mally included? It is always worth while to group facts anew, 
and to show their manifold relations. But a fresh grouping 
needs careful handling; the facts must be on a logical string, 
and that string must be obvious throughout. In this case, the 
grouping would be, in the main, carbon and its oxides, coal, 
the hydrocarbons, illuminants, flame, furnaces, fractional dis- 
tillation. The hydrocarbons form a big subject, of course, but 
it would not be necessary to include here more than an elemen- 
tary study of, say, methane, ethylene, acetylene, and one or 
two others. 



Chemical Theory 

In view of the ever-increasing mass of facts in chemistry, 
many of them of the highest importance, what should be the 
future position of chemical theory in our teaching? Should it 
be given a subordinate position? should it be omitted altogether? 

Either of these courses would mean that chemistry would 
cease to be a science. The facts are the bricks, theory is the 
cement, of the whole edifice. The facts without the theory are 
just a heap of bricks, not a building. Theory must be taught, 
but it must be taught in such a way that learners can see clearly 
how its successive points emerge from our method of classifying 
facts. 

The centre of public interest at the present day lies in the 
new discoveries and hypotheses of physics the structure of 
the atom, the theory of relativity, the theory of quanta, the 
existence of the aether, the results of the examination of crystals 
by means of X-rays. There is relatively little public curiosity 
in regard to the advance of chemistry; a little in dyes and in 



164 SCIENCE TEACHING 

poison gas, perhaps; hardly any in agricultural chemistry , 
the most important branch of all from the national point of 
view. 

Some authorities are of opinion that chemistry is fated to 
become a branch of physics, and to lose its own peculiar dis- 
cipline. Our knowledge of the internal structure of the atom 
has advanced with such rapidity that chemistry certainly may, 
in time, become a deductive science. But that time is not yet. 
Chemistry is still an experimental science yielding conclusions 
by inductions from observed facts, and most of its long- 
established hypotheses still survive merely as hypotheses and 
nothing more. 

And yet our confidence in these hypotheses is increasing. 
Why? 

Consider Dalton's hypothesis. Dalton's atoms were purely 
imaginary. They were used to explain known facts and to predict 
new facts. Nobody claimed them to have a real existence. But 
gradually the conception of atoms and molecules was found to 
fit a larger and larger field of facts; confidence grew, and mole- 
cules with their families of atoms tended to become real, and 
the discovery of radioactivity confirmed, to an extraordinary 
degree, the theoretical view advanced a century before. Not 
only so, but the study of the films of fatty acids and similar 
substances on the surface of water has shown that the properties 
of such films can be accounted for only by asserting the reality 
of those chains of atoms which had previously been hypotheti- 
cally assumed to exist in order to explain the structure of organic 
compounds. The experimental confirmation of the hexagon 
formula for benzene was a particularly great triumph. Finally, 
there is the tetrahedral arrangement around a carbon atom, 
devised to explain optical isomerism. Modern X-ray methods 
show that the structure of crystals of corresponding substances 
is fully accounted for by assuming that the benzene hexagon 
and the tetrahedral carbon linking are actually present. 

Since the atom, the molecule, the chains and linkings repre- 
sented in the graphic formulae of organic compounds, the hexa- 
gonal ring in aromatic substances, and the tetrahedral carbon 



CHEMISTRY 165 

atom, w$re all first invented merely as working hypotheses for 
co-ordinating groups of experimental facts, and since their 
actual physical existence seems now to have been confirmed by 
entirely independent means, ought we to tell pupils dogmatically 
that atoms, molecules, and the rest are now known to have an 
objective existence? 

The answer is in the negative. Let the teacher safeguard 
himself by saying " there is now good reason to believe that " 
atoms really exist. After all, the evidence is still very largely 
inferential, and the final conclusion is due to many lines of 
different evidence all gradually converging to one point, some 
of these lines consisting of both facts and hypotheses, but the 
whole mass of evidence proving well-nigh irresistible. It must 
be remembered that pupils are not in a position to marshal all 
the evidence, or even to grasp its significance when marshalled 
for them. It is a sound working rule not to advance an hypo- 
thesis until the available facts warrant it. Teachers cannot be 
too insistent in telling their pupils to be cautious about draw- 
ing deductions from the evidence obtained from experiments. 
There is always a danger that the beginner will assume that 
the facts depend upon theory instead of theory upon the facts. 
The pupil must know his facts first. 

In a well-known standard text-book on chemistry, the 
author, discussing the theory of electrolytic dissociation, says: 
11 The facts can not only be interpreted by means of this theory, 
but are a necessary consequence of it." The second part of 
the statement implies that the facts occur as a mere consequence 
of a pre-existing theory. Such a statement is grotesque. Had 
the author said that new facts had emerged from an investi- 
gation undertaken on the strength of the assumption that the 
theory was true, his statement would have been acceptable. 

What principle is most fundamental in all chemistry work? 
What facts form the basis of our performance and interpretation 
of every chemical experiment? 

Is it the atomic hypothesis? Chemistry teachers used to 
think so, but they were teachers of an age that is past. 

Is it the principle of definite proportions? This presupposes 



166 SCIENCE TEACHING 

the conception of compounds, and the idea of elements and 
compounds is therefore more fundamental. 

Is this idea of elements and compounds the answer to our 
first question? No, for we cannot recognize a compound except 
by obtaining from it two or more substances with properties 
which distinguish them from one another and from the parent 
substance. 

It is these distinguishing properties that give us an answer 
to our question. 

The basis of all chemical work, then, is the fact that each 
substance has its own set of physical properties by means of which 
the substance is recognized and by the use of which the substance 
is separated from other substances when necessary. The main 
object of every experiment is to produce new physical phenomena 
for purposes of observation , and to discuss these observations in 
terms of physical realities. 

At what stage may the atomic hypothesis most usefully 
be introduced? The answer is, when we have accumulated the 
particular set of facts the hypothesis was primarily designed to 
explain. The central fact of that particular set was that the 
proportions by weight in which a given element enters into all 
sorts of combinations may always be expressed by a fixed 
number, or by whole multiples of this fixed number. Hence, 
the hypothesis should be introduced when experiments dealing 
with combining proportion by weight have been performed, 
and the results are discussed. In other words, it should be 
introduced for explaining the quantitative laws of chemical 
combination. 

May it be used at an earlier stage, for instance to explain the 
bare facts of chemical combination and the qualitative features 
associated with it? Consider the simple case of the com- 
bination of Cu and S to form CuS. The boy knows the pro- 
perties of Cu and of S, and he expects the properties* of the 
combined mass to be a sort of average of those properties. 
But he finds they are wholly different. Will this new mystery 
be cleared up if he is told to think of the Cu as consisting of 
tiny bits (atoms) and the S as consisting of tiny bits, and of 



CHEMISTRY 167 

each tiny, bit of Cu becoming attached to a tiny bit of S; and 
that when the tiny bits are attached in this way, the properties 
of the united little bits will be entirely unrelated to those of 
the previously separate little bits? Is an intelligent boy expected 
to believe that the rearrangement of these invented and imagined 
little bits can explain changes of properties? Would the boy 
not be justified in telling his teacher to tell that story to his 
grandmother? 

How can the atomic hypothesis, as commonly presented 
to beginners, adequately explain the nature of the tendency to 
combine, or the mode of combination, or the new properties 
of the product of combination, or the heat developed during 
the process of combination, or indeed anything save the pos- 
session, by each element, of a special unit of weight which it 
employs in all its combinations? 

If we invite a beginner to believe as a fact that diverse 
atoms become united in pairs, and that the properties of the 
combinations are unrelated to those of the constituents, and 
if we invite him to associate those two inconsistent ideas every 
time substances are combined in the laboratory, shall we not, 
as a result of persistent suggestion, finally hypnotize him into 
a frame of mind in which logical consistency is no longer a 
test of credibility? Is it surprising that the intelligent layman 
sometimes scoffs at " scientific " reasoning? 

Let the teacher say as little as possible about the relation 
of the atomic hypothesis to those things which it was not 
primarily devised to explain. 

Observation and experiment are the only method of obtaining 
facts, and no facts can be safely obtained either by inferences 
from, or by interpretation of, laws. Observation in chemistry 
consists in noting the specific physical properties of substances,, 
as revealed by experiments. 

Very little theory should be attempted until after the great 
generalizations of chemistry have been established on an 
experimental basis the laws of constant, multiple, and reci- 
procal proportions and the law of Gay-Lussac. Dalton's hypo- 
thesis and Avogadro's hypothesis are now necessary to explain 



168 SCIENCE TEACHING 

the groupings that led to these laws, and theoretical considera- 
tions must therefore now step in. As the work advances, the 
atomic theory is further and further developed. 

There is no objection to the comparatively early use of 
formulae and equations, if it be made clear that they are merely 
a shorthand registration of experimental results, and nothing 
more. Early in the course they can have no real quantitative 
significance. 

Valency is a subject which often gives trouble to beginners. 
It should give none if its experimental basis is made clear 
that it is simply a consequence of the choice, from amongst 
possible combining weights, of the particular atomic weight. 

If organic chemistry is formally included in the school 
course, to what extent should the theory of the subject be 
pursued? The answer leaves little room for doubt. It should 
be pursued just far enough to enable the learner to understand 
the broad principles underlying the grouping of organic com- 
pounds. The boys must have clear notions of stereo-isomerism, 
and, generally, of the architecture of the organic molecule. 
But do not conceal the few things that really matter, and they 
are very few, behind a smoke screen of those elaborate formulae 
so dear to the heart of the expert chemist. 

It may be well to remember that, into the great industries 
which have been founded by chemistry, and into the prac- 
titioner's day-by-day analytical work, the atomic theory as 
such hardly enters. Chemistry as an art can be taught without 
any reference to the atomic theory. But chemistry as a science 
is on a different footing, for here its processes have to be placed 
on a rational and consistently logical basis. And it is chemistry 
as a science which is the chemistry of schools. In schools we 
teach chemistry partly for its own sake but also, at least equally, 
for the sake of the almost unequalled intellectual discipline 
which the subject, as a science, exacts from its followers. 



CHEMISTRY 169 

> Still More Snags 

i. PHYSICS IN CHEMICAL EXPERIMENTATION. Admittedly 
all chemical observation consists simply in the noting of physical 
occurrences, and in interpreting them in accordance with 
physical principles. Curiously enough those parts of physics 
which are most needed in chemistry are precisely those which 
receive but little attention in the average physics course pre- 
scribed for schools. 

A boy is told, say, to heat KCIO%, to observe what happens, 
and to record his observations. The boy writes down: " The 
substance melted, and then it boiled/' How can we find fault 
with him for assuming that the action is similar to the action 
of the heating of ice? Outwardly, to the untrained observer, 
the appearances are at first much the same. Why should the 
boy continue with the heating of the chlorate, unless he is 
told to do so? Why should he not assume that, if the boiling 
is continued, the substance will disappear much in the same 
way as water disappears? Or, if he has had previous experi- 
ence of water of crystallization, why should he not assume 
that the substance has " melted " in its own water of crystalli- 
zation? If by chance he observed that the agitation of the 
liquid did not cease when the flame was removed, he might 
begin to suspect that he was not dealing with a case of simple 
boiling, provided that he was already familiar with the nature 
of boiling. The changes in the consistency of the material would 
puzzle him, and as for the giving off of oxygen, why should 
he suspect it? Clearly the boy should have been given detailed 
directions, but the experiment presupposes that a boy has been 
already trained to recognize and to understand the phenomenon of 
ebullition. 

Again, how is a pupil to study the action of strong HCl on 
iron and copper, unless he knows the distinction between the 
boiling of a liquid, the evolution of a gas from a solution (both 
of which might happen in the case of copper), and the evolution 
of hydrogen (which will occur with the iron)? 

Again, pupils often find difficulty in distinguishing gases 



170 SCIENCE TEACHING 

from solids and liquids. They do not know that gases do not 
disperse light but transmit it, and thus they think that the fog 
issuing from a locomotive is entirely gaseous. A familiarity 
with the relations of matter to the dispersion of light is essential 
to the understanding of many experiments in chemistry that 
involve the production of fumes of some kind. The same field 
of knowledge is involved in understanding the difference between 
solution and suspension. 

How is a pupil to understand that, say, P 2 O 5 is not a gas^ 
if, the first time the phenomenon is encountered, the behaviour 
of the substance is not compared carefully with that of a gas? 

Again, consider the experiment of burning hydrogen in air 
to form water. Extinguish the jet, and hold a cold beaker 
against the jet of unlightcd gas; moisture is still formed. This 
always puzzles a class of boys. Some will suggest that the 
water comes from the combination of the hydrogen with the 
oxygen in the air, showing that they have failed to realize the 
significance of lighting the jet. Others will suggest that it 
arises from condensation of moisture in the atmosphere, though 
they cannot explain this. Only rarely will a boy give the real 
reason that the flask contained a liquid which was warm and 
consisted largely of water through which hydrogen was passing 
and that therefore the issuing gas consisted of a mixture of 
hydrogen and water vapour. Beginners are not likely to realize 
that the gas must be dried if the experiment is to be fair. 
The lesson is so valuable that the thoughtful teacher will not 
dry the gas until the lesson has been learnt. 

Thus it all comes round to this that a course of elementary 
physics must precede chemistry. All chemical experimentation 
involves the observation of new physical phenomena, and in 
order to recognize these phenomena pupils must have had a 
suitable previous training. A good deal of incidental instruction 
in physics will, however, necessarily accompany every chemistry 
course, though such instruction will be less of a formal kind 
than that of a kind which consists in drawing attention to the 
fact that the work in progress involves the application of certain 
physical principles already taught. 



CHEMISTRY 171 

2. INADEQUATE LABORATORY DIRECTIONS. In a certain 
" laboratory companion ", the following exercise is given: 
" Write down what you observe when concentrated sulphuric 
acid acts on crystals of potassium iodide/* Such directions 
are altogether inadequate, and failure is inevitable. The pupil 
ought to be told to powder the crystals, just moisten with 
the acid, and warm. But, even so, the result is bound to baffle 
him. He observes fumes in the air outside the mouth of the 
tube, a violet-coloured vapour inside the tube, a brown film 
on the walls of the tube, an odour (SO 2 or H 2 S or both), and 
perhaps a yellow sublimate (sulphur). Unless he is warned 
he may assume that one body has all these properties. Without 
detailed guidance, he will never realize that from three to five 
different products have resulted from the action, and certainly 
he may not yet have met with some of them. The directions 
should be given in much greater detail in order that an investi- 
gation may be made systematically. Bat such an experiment 
would be unsuitable unless the pupil had previous knowledge 
of the properties of the different substances resulting from the 
action. 

In any chemistry course, the succession of experiments 
should, as nearly as possible, form a natural sequence. A boy 
might, for instance, be legitimately asked how he would separate 
a mixture of II and CO 2 provided he was already familiar with 
the properties of the two gases. He ought then to be able to 
suggest one or more ways of removing one of the constituents 
of the mixture. A well-taught pupil should be able to " think 
chemically ", and apply his knowledge in a rational manner. 
Such a pupil will see, when a piece of sodium is thrown upon 
water, something more than the antics of the metal. 

3. NEGLECTED OPPORTUNITIES FOR ILLUSTRATING CHEMICAL 
ACTION. A whole lesson is sometimes kept too strictly within 
severely academic limits. Whenever possible, borrow illus- 
trations from everyday life and illustrations from technical 
processes. For instance, illustrate oxidation by the way in 
which paint dries through the absorption of oxygen by the 

(K72) 13 



172 SCIENCE TEACHING 

solidifying oil; reduction, by photographic developers; rever- 
sible actions, by the storage battery; osmotic pressure, by root 
pressure in plants; dissociation of the reversible kind, by lime- 
burning; displacement of metals, by toning in photography; 
solution, by alloys. And so generally. 

4. QUALITATIVE ANALYSIS. The possible educational value 
of this work is much reduced by the present-day tendency to 
neglect preliminary " dry tests ". These tests, especially for 
the identification of single substances, may afford the learner 
so much evidence that the subsequent " wet " work is little 
more than confirmatory and may be quickly done. Heating 
on charcoal, heating in bulb tubes, perhaps heating with con- 
centrated H 2 SO 4 , borax bead tests, ignition on platinum wire, 
sublimation, all these and several others of like kind give the 
pupil a knowledge in which he soon feels great confidence. 
Valuable clues, if nothing more, almost always emerge from 
these tests, and the time for the complete analysis is greatly 
reduced. I have often seen pupils, who had been well trained 
in this preliminary work, obtain correctly in a very short time 
the several constituents of a mixture commonly thought to be 
" difficult ", whereas other pupils who depended entirely on 
their " wet " separation tables took much longer and were 
seldom altogether successful. 

5. GRAVIMETRIC VERSUS VOLUMETRIC WORK. In his Prac- 
tical Chemistry, Mr. Holmyard devotes fifty- three experiments 
(41 pp.) to volumetric analysis, and only three (4 pp.) to gravi- 
metric analysis. I am not very happy about this proportion. 
Mr. Holmyard says that gravimetric analysis " is not so con- 
venient as volumetric analysis and requires considerably more 
skill; it is therefore a very good training for the young student, 
and should on no account be omitted. At the same time the 
operations are often rather lengthy/' 

On several occasions I have given a class the same estimation 
exercise to do, half to do it volumetrically, half to do it gravi- 
metrically, and I have invariably found that the latter had by 



CHEMISTRY 173 

far the clearer understanding of the problem in hand. There 
seems to be a greater simplicity about gravimetric methods, 
a simplicity which inspires greater confidence in the final 
result. And some of the older text-books on quantitative 
analysis, Professor Thorpe's and Mr. Newth's, for instance, 
leave nothing to be desired in the lucidity of their detailed 
instructions for gravimetric analysis. In volumetric work, the 
simpler titrations soon become at least as mechanical as the 
much criticized qualitative analysis. Still, volumetric work 
has its good points, educationally, and it is bound to find an 
important place in any school chemistry course. Mr. Holm- 
yard's treatment of the subject is all that can be desired. 
Another admirable little book is that by Mr. J. B. Russell. 

6. FORMUL/E. We have already referred to that invaluable 
little book Experimental Proofs of Chemical Theory by the late 
Professor Ramsay, and we criticized its method of establishing 
the Law of Charles. But it has to be borne in mind that a 
university professor usually writes a book for students already 
familiar with the elementary parts of the subject. Detailed 
instructions concerning experiments for establishing principles 
ought not, therefore, to be necessary, though for beginners 
such instructions are naturally the normal thing. Thus, if and 
when this particular book is used in schools, the subject-matter 
provided has to be considerably supplemented. 

An example from Professor Tilden's Chemical Philosophy 
may usefully be considered. The problem is to establish the 
formula of a compound which, when analysed, gave the follow- 
ing result: C, 37-20 per cent; H, 7*90 per cent; Cl, 54-95 
per cent. The author then divides these percentages by the 
atomic weights, and then each of these quotients by the least 
quotient (all in accordance with accepted procedure), thus 
arriving at the formula C 2 H 5 C1. As might be expected, the 
instructions are perfectly sound as far as they go, and doubt- 
less an advanced student would understand the rationale of 
the whole process. But no hint is given why the percentages 
are divided by the atomic weight, or why the three quotients 



i 7 4 SCIENCE TEACHING 

are divided by the least. An intelligent boy would, if he 
followed out the instructions, doubtless evaluate the formula, 
but the work he had done would have no physical significance 
to him. 

Contrast with this a similar problem with explanatory 
arguments specially provided for school boys. We select Mr. 
Holmyard's 3rd, 4th, and 5th sections of his chapter on Deter- 
mination of Formulae (Organic Chemistry). The sections are, 
calculation of empirical formula, calculation of molecular weight, 
calculation of true formula. The empirical formula for ethyl 
alcohol is established, then follow arguments concerning the 
true formula. The arguments are lucidly set out, and the 
learner (presumably belonging to a Sixth Form) is able easily 
to understand what he is about. 

7. CATALYSTS. Do not make the pretence of explaining 
to beginners such a process as catalytic action. It is enough 
to tell them that catalysts are speed-modifiers, faster or slower. 
Hypotheses as to their nature may come later. If physiology 
is taught, a similar remark will apply to enzymes, which may 
be regarded as organic catalysts, serving to stimulate chemical 
reaction involving organic compounds. Ptyalin in saliva and 
pepsin in gastric juice are common instances. 

Logical or Psychological Order? 

This question arises in the teaching of all other branches of 
science, as well as chemistry. It is a good general rule so to 
arrange the facts to be taught that they are presented in the 
order of difficulty of comprehension. The ordinary text-book 
in chemistry often makes H 2 O 2 follow close on the heels of 
H 2 O, because of the close relationship in composition. Logically 
this is defensible enough, but H 2 O 2 is a substance differing 
greatly from water, and the chemical actions illustrating its 
behaviour are often very complicated. The wise teacher there- 
fore postpones H 2 O 2 , or even eliminates it entirely. Again, 
standard text-books commonly classify all the chlorine com- 



CHEMISTRY 175 

pounds in one group, and describe them in succession. But 
the result is quite different when we classify the compounds 
according to the intrinsic difficulty of understanding the re- 
actions of each. The study of the element chlorine is easy 
enough, so is the union of chlorine with other elements. But 
when we reach hypochlorous acid, with its habit of decomposing 
in three different ways, we have to deal with a topic very much 
more difficult to understand. It should therefore be postponed. 
But, as far as possible, the psychological order should be the 
logical order. If the teacher cuts himself adrift from the logical 
order, or even very much from the traditional logical order, 
he is seeking trouble. He should adhere to a logically worked- 
out system as far as this is consistent with psychological prin- 
ciples, lest his building powers should prove unequal to the 
task of erecting a structure to take the place of that he has 
demolished. 



The History of Chemistry 

No course of school instruction in chemistry is complete 
unless it includes at least an outline of the history of the subject. 
Some writers of modern text-books include a good deal of 
history incidentally. Mr. Holmyard is one. Dr. Bauer's History 
of Chemistry is particularly attractive in that it groups the 
subject under periods the chemistry of the ancients, the 
period of alchemy, medical chemistry, phlogistic chemistry, 
Lavoisier, developments in organic chemistry, present-day 
chemistry. Let the teacher always try to group together workers 
in the same field, e.g. Grotthus, Hittorf, Pfeffer, Ostwald, van 
t'Hoff, Arrhenius. And do not forget the quarrels of rival 
schools: how, for instance, Kolbe personally insulted van t'Hoff. 
Boys like to read about the quarrels of great men of science, 
and it helps to impress them with the fact that hypotheses are 
only hypotheses after all. Readers of Nature are well aware 
that there are living men of science who dread the discovery 
of new facts which will dethrone a pet hypothesis that made 
them famous years ago. 



j 7 6 SCIENCE TEACHING 

Another point: never give boys reason to think* that all 
scientific discoveries are due to Englishmen. Think of the 
great chemists that even Sweden has produced. 



Text -books and New Books 

The value of a good text-book lies in the fact that it is a 
source of knowledge arranged systematically. It furnishes a 
definite record, and enables the pupil to acquire needed infor- 
mation speedily. But any book has its limitations. It omits, 
and inevitably must omit, the description of a vast number of 
the physical details which are, after all, the native language of 
the science, so to speak. This is where the private student is 
so greatly handicapped. 

The chemistry teacher who thinks he can teach his subject 
merely by transferring the contents of a text-book into the 
heads of his pupils is under a great delusion. The best book 
has to be supplemented in a hundred ways. 

Books outside the ordinary text-books, especially books with 
a human interest, must be recognized as playing a necessary 
part of a pupil's training in chemistry. For instance, Davy's 
and Faraday's accounts of their own researches are always of 
the greatest interest to boys, and, incidentally, the boys learn 
much from them, especially about methods of investigation. 
From the point of view of interest, such books are on a par 
with the best detective stories. They are detective stories. 

Always keep a look-out for new books written by well- 
known teachers, even though you may decide you will not 
adopt them. Such books nearly always contain something worth 
learning, some new point of view, something unconventional, 
something rather contrary to accepted traditions, something a 
little provocative. The new book by Messrs. Dootson and 
Berry, for instance, is full of new points. The chapter on the 
ionic theory is particularly good, and such minor matters as 
the extreme sub-divisibility of matter, and the superior limit 
of molecular dimensions are treated in such a way as to make 
an immediate appeal to the learner. Many teachers will be 



CHEMISTRY 177 

inclined % to argue, perhaps hotly, about some of the methods 
of presentation, but a book that provokes discussion is always 
useful. Some of Mr. Holmyard's methods are bound to pro- 
voke discussion: so much the better. We are all apt to lean 
a little too heavily on tradition; that way safety lies so we 
unconsciously argue. 

Keep in the school library such books as Dr. Philip's 
Romance of Modern Chemistry, Arrhenius's Chemistry in Modern 
Life, Rogers's Industrial Chemistry for Students and Manu- 
facturers, and let boys refer to them for special points to 
illustrate principles, to suggest new applications, to see a thing 
from another point of view. Such books are not written on 
traditional lines, and on that very account are specially valuable. 
Another excellent work of reference is Tilden's Discovery and 
Invention in the Twentieth Century. Teachers who know noth- 
ing of American universities will have something of a shock 
when they read in this book an account of, say, the extent of 
the chemistry buildings and of the professorial staff in the 
University of Illinois. 

Every teacher of chemistry should read Professor Arm- 
strong's article on chemistry in the 1926 edition of the Encyclo- 
paedia Britannica. It throws more light on the inner nature of 
the whole subject than any standard work I have read. In 
particular, a teacher may glean from it many useful hints as 
to the best method of approach to organic chemistry. 

Laboratory First-aid 

Accidents will happen, and the chemistry teacher must 
always be prepared for emergencies. Let him keep a special 
cupboard for first-aid appliances, and, pasted up in the cup- 
board, a plainly written list of the commoner accidents and the 
remedies to be applied. The cupboard should contain bandages, 
lint, boric wool, oiled silk, court plaster, scissors, solution of 
iodine, boric acid solution, boric acid powder, sodium bicar- 
bonate, carbolic acid, picric acid (for powdering over a phos- 
phorus burn, after cleansing with a weak wash of carbolic), 



i 7 8 SCIENCE TEACHING 

ammonium hydrate, alcohol (for inhaling the vap9ur, after 
chlorine or bromine irritation), and a clean wash-bottle with 
clean water frequently renewed. The contents of the cupboard 
should be kept exclusively for use in accidents that may occur 
in the laboratory or lecture-room. The key of the cupboard 
should remain in the lock whenever the laboratory is in use, 
and it should be somebody's special business to see that this 
is done. It is always advisable for the chemistry teacher to 
submit his first-aid scheme to the school medical officer. That 
way lies safety. 

All pupils may be instructed thus far: the first-aid remedy 
for burns caused by acids and alkalies is neutralization. For 
acid burns, wash with water and apply solution of a weak 
base, say sodium carbonate, or, if this is not available, then 
lime water or dilute ammonia solution; for alkali burns, \vash 
with water and apply solution of a weak acid, either saturated 
boric acid or very weak acetic acid. 

Remember that first-aid is only first-aid. Unless the 
accident is trifling, the patient should be sent off at once to 
a surgeon. Actions at law are apt to be unpleasant, no matter 
how careful the teacher may have been, no matter how careless 
and disobedient an injured boy may have been. 

Terminology 

Give pupils the origin of such terms as ethyl, i.e. et(her)hyl; 
amine, am(monia)ine; aldehyde, al(cohol)dehyd(rogen); acetone, 
acet(ic)one. A score of Greek roots will explain a hundred 
terms. But chemists cannot be forgiven for adopting such bas- 
tard terms as ester and ketone. 



BIOLOGY 179 

CHAPTER XIV 

Biology 

The Neglect of Biological Teaching 

It behoves all science teachers to help educate public 
opinion as to the vital importance of a knowledge of biology. 
As a branch of science, biology is, even now, commonly 
associated with a perfunctory and amateurish study of an 
emasculated botany, a harmless hobby suitable for children 
and slow-witted girls, not a virile discipline for the intellectual 
girl and boy. Biology as a subject for the adolescent connotes 
something very much more than what is commonly known as 
"Nature Study". 

The Report of the Prime Minister's Committee emphasized 
the need for the inclusion of biology in every secondary school 
course. It was considered that the ground to be covered before 
the age of 16 should include, first, the main facts as to the 
relations of plants and animals to their surroundings, and as 
to the changes in material and in energy involved in their life 
and growth; secondly, the main anatomical features of the 
higher plants, the elementary physiology of plants, and some 
quite general knowledge of animal metabolism. Between 16 
and 18, systematic work in zoology, including the dissection 
of animals and the use of the compound microscope, might, 
the report suggested, form a suitable basis for the work to be 
done. 

The Committee of British Zoologists, in their draft report 
on the position of animal biology in the school curriculum, 
urged that the general aim of school studies in biology should 
be to inculcate a sound appreciation of the natural laws which 
govern the lives of human beings no less truly than they do 
those of other animals and of plants; that the basis of the 
study should be close observation of plants and animals in 



i8o SCIENCE TEACHING 

relation to their natural environment and not as self-contained 
entities; and that morphological study should be undertaken 
less for its own sake than for that of its fundamental importance 
in the study of organic function. The committee suggested 
that the work of the lower Forms should consist mainly of direct 
observational study of living plants and animals; that in the 
middle Forms it should be correlated with elementary physics 
and chemistry; that a special feature should be made of simple 
experiments illustrating the fundamental processes of respira- 
tion, assimilation, &c., in plants and animals alike, and that 
their essential similarity to the corresponding processes in the 
human subject should be emphasized, and that the idea of 
evolution should be implicit; that in the higher Forms (pupils 
above 16), biological work might be conducted along the 
separate lines of botany and zoology, and more detailed mor- 
phological study be undertaken in both, but that the greatest 
importance should, throughout, be attached to the elucidation 
of the functioning of organs and of the organism as a whole. 

All this is most admirable advice, but it might perhaps 
have been given with greater emphasis. The past general neglect 
of biological study in secondary schools largely explains why 
the cultivated classes of the country are so ignorant of bio- 
logical principles. Comparatively few educated people have 
a grasp of those principles, even of the principles which are 
most directly related to human welfare and right living. Fewer 
still seem to be aware how the laws of heredity are now recog- 
nized as of vital importance, not only for increasing and im- 
proving supplies of agricultural products but for human life 
itself. It is undeniable that men aspiring to a place in national, 
or even local, leadership ought to have a firm grasp of all 
available knowledge of those laws which underlie human life 
and human evolution. They ought also to understand what 
an enormously important part biological science plays in the 
modern civilized state. The provision of food for the com- 
munity crop-raising, stock-breeding, the production of dairy 
products, fisheries, the preservation of food by canning and 
freezing, and so on is obviously an immensely complicated 



BIOLOGY 181 

system oS applications of biological science. So also with the 
maintenance of the health of the community the prevention 
of disease, the war on parasitic microbes, and the cure of disease 
by the modern methods of medicine and surgery those are 
also obviously applications of biological science. 

Main Principles of Biological Instruction 

But all these things are mere applications of principles to 
be taught in a course of school biology. In drafting such a 
course, what are the main principles to be kept in view? On 
this there is general agreement thus far: (i) the great fact of 
evolution and its far-reaching implications, especially the 
struggle for existence in nature and the elimination of the 
unfit; (2) the great fact of inheritance the fact that the child 
repeats the characters of the parent, physical, mental, and 
moral, but that this repetition is never so complete as to 
amount to identity as regards such characters; (3) the biology 
of communal life, both as presented by communities of social 
insects such as bees and ants, and as presented by cell com- 
munities constituting the bodies of the higher animals. It is 
of the utmost importance for the pupil to understand the three 
great principles of communal evolution: (i) increase in the 
size of the community; (2) increased specialization of its con- 
stituent individuals; (3) increased perfection of the organization, 
by which the constituent individuals are knit together into the 
communal individuality of a higher order. Then, but not 
before, the pupil may appropriately approach the study of 
human society, where the same principles are at work, and 
evolution still proceeding. 

When a teacher is drafting a biological course, all these 
principles will be kept steadily in view. But they are not prin- 
ciples which will appear in the early lessons; rather they form 
the general aim and purpose of the course as a whole. The 
course completed, the principles will have been worked out. 
During the actual working out of the course, necessary facts will 
be accumulated, and subsidiary principles will be established. 



i8z SCIENCE TEACHING 

The planning out of a course to meet these requirements 
is exceedingly difficult, especially if it is to be as exacting as a 
course in physics or chemistry. The subject is so big, the 
available time so little. Clearly it is not possible to do more 
than make a small selection from the vast number of known 
facts, a selection nothing like great enough for generalizations 
to be based on them, but enough to illustrate and typify. 
There is consequently always the danger that the teaching may 
tend to become dogmatic, and yet, of all the subjects taught in 
school, biology is the very last to be doled out as unassailable 
dogma. Biological theory is seldom more than an affair of 
possibilities; rarer, of probabilities. Occasionally a biological 
hypothesis receives universal acceptance; much more often 
it is tinged with doubt and uncertainty. 

Biology a Difficult Subject to Teach 

Biology naturally falls into a series of allied studies. These 
studies are concerned with the characteristics of living organisms, 
their forms and parts, the various functions which the parts 
discharge, the physical relations which the forms have with one 
another and with their environment, their genetic relations, 
and their geographical distribution. Living organisms seem 
to have the power of self-maintenance, and the power of pre- 
serving an individuality. A living organism takes nutriment, 
grows, and reproduces itself. 

For investigation purposes, we are driven to treat the living 
organism as a physico-chemical mechanism, though of course 
the organism is something much more than the sum of all its 
parts and their physico-chemical relations; it is a unified and 
purposeful individual. Every organism (unicellular organisms 
excepted) is an association of cells, each cell living its inde- 
pendent life but each contributing in some special way to the 
life and maintenance of the organism as an individual whole. 
This is one of the first things for a pupil clearly to understand. 

How the physical and the psychical are related in an 
organism we do not know. That they are related is certain. 



BIOLOGY 183 

The change in the moral character of a man is sometimes the 
effect of a brain-lesion due to a blow on the head; bad news 
may bring about a psychical disturbance which results in a 
marked physical disturbance of the body, temporary or per- 
manent. But the relationship is an unsolved mystery. 

As far as we can tell, an animal which has just died is 
chemically identical with what it was when alive. It serves 
no good purpose to " explain " things by the supposed presence 
in a living organism of a " vital force ", of an " entelechy ", 
or of some other imaginary, elusive, responsible, working prin- 
ciple. It is much more honest to tell the pupil that we don't know. 
Abstain from talking to pupils about materialism, vitalism, or 
any other -ism. The teacher's business is to explain how living 
things act and to say candidly that he does not know why they 
so act. 

The experimental difficulties in biology are great. The 
extreme complexity of structure and of function of the living 
organism makes it very difficult to isolate any particular part 
we wish to examine. Such isolation is usually possible in 
physics and chemistry, but in biology the simplest experiment 
is complicated by the fact that the thing being experimented 
with is alive, with the consequent possibility of the presence of 
all sorts of unsuspected disturbing factors. 

Always impress upon pupils the fact that the great majority 
of the vast number of ascertained facts in biology, and many 
of the great generalizations, are not the results of work done 
in the laboratory but of work done outside it the work of the 
great naturalists who as travellers have examined living or- 
ganisms, their habits, distribution, and environment, all on a 
large scale. Darwin and Wallace are examples. Pupils cannot 
understand too clearly how a biologist is, first of all, an out- 
door naturalist. The effect of a too exclusive occupation with 
laboratory experimental work tends to be narrowing, though its 
importance cannot be over-emphasized. We cannot but respect 
a man who devotes a life-time to the study of, say, the neurology 
of the Aphides, but to call him a biologist is to stretch courtesy 
almost to the breaking-point. 



184 SCIENCE TEACHING 

Biology as a Group of Allied Studied 

The first and most obvious division of biology is into the 
two studies of plants and animals, BOTANY and ZOOLOGY, respec- 
tively. The broad distinction for pupils to note between plants 
and animals is that plants contain chlorophyll and cellulose, and 
make their own starch and sugar, while most animals have to 
depend, directly or indirectly, upon plants for their food. 
But both plants and animals may be considered from two points 
of view: (i) that of the anatomist who dissects out the large- 
scale organs, and the histologist who examines the minute 
tissues; both are interested in the forms of animals and plants 
as wholes, in structures, connexions, positions. Their subject 
is MORPHOLOGY: it is the static side of biology. (2) That of the 
physiologist, who deals with the dynamic side of biology, the 
aspect expressed by the term function the study of the activity 
of the various organs, the activities of tissues, the active life 
of individual cells, the metabolism of the protoplasm. Thus 
morphology is contrasted with PHYSIOLOGY. 

To the study of morphology belongs the study of anatomy 
and histology of extinct species, termed PALAEONTOLOGY. 

Then, again, we have the study of the early stages in the 
growth of the organism, its organs, and its tissues. This study, 
EMBRYOLOGY, includes both the morphology and the physiology 
of the developing organism. 

Both palaeontology and embryology are in close relation with 
the racial and evolutionary aspects of biology. 

Then, again, although life is limited to the individual, it 
is continued in the race, and this suggests the studies of EVOLU- 
TION and HEREDITY. 

The study of the diseases of organisms has for its basis 
the subject of BACTERIOLOGY. 

Both morphology and physiology will naturally be included 
in any course of either botany or zoology. 

All the biology that is likely to be taught in schools will 
thus be included under these headings: botany, zoology, 
human physiology, embryology, palseontology, evolution, here- 



BIOLOGY 185 

dity, bacteriology, and these form the subjects of the next few 
chapters. 

Genetics is virtually another term for heredity. Ecology, 
the relation of organisms to their environment, should be 
treated as an ordinary section of botany and of zoology. So 
should the geographical distribution of animals. 

The greatest advance in biology in recent years has been 
made in the study of the cell. In fact, biologists are now 
beginning to think of life in terms of cells, and they are con- 
centrating their attention on the process of cell division, feeling 
sure that wonderful secrets lie buried there. The genetical 
process of division is the central phenomenon of physiology, 
and is perhaps the key to variation and heredity. 

Pupils should know something of the lives of the great 
naturalists and biologists Linnaeus, Cuvier, Buffon, Owen, 
Lamarck, Mendel, Darwin, Wallace, Huxley, Pasteur, Weis- 
mann, and others. 

Schools which cannot find time for the study of the separate 
subjects considered in the next few chapters should take up 
a course of a more general kind. For this purpose there is no 
better book than Haldane and Huxley's Animal Biology. The 
writers, who are, of course, eminent authorities on the subject, 
have packed into some 340 pages the essentials of all branches 
of the subject. They describe things remarkably clearly, and 
their illustrations are so good that there is no difficulty what- 
ever in following up their argument. But teachers who take 
up a general course of this kind should remember all along 
that plant and animal life form the two complementary halves 
of a single subject, and that from the outset both must receive 
attention. 

Before proceeding with the chapters on the subdivisions 
of biology, we must deal with the general question of biological 
classification and terminology. 



i86 SCIENCE TEACHING 

CHAPTER XV 

Biological Classification and Terminology 

Main Principles of Biological Classification 

Ask a boy if he can classify " races of men " logically, in 
accordance with the common usage of the term race the white 
race, the Latin race, the Irish race, and so on; and thus lead 
him to see how unscientific the common assumption is that 
race is an affair of pigmentation of the skin, or of religion, or 
of geographical position, or of temperament. Show him that 
criteria of race are necessarily physical, including, in particular, 
such morphological features as the shape and proportions of 
the head, the qualities of the hair, skin, nose, and eyes, stature, 
and so forth. But since no bodily characters are wholly exempt 
from adaptive modifications, there does not seem to be any 
single characteristic that absolutely marks off one race from 
another. And even if we could classify men satisfactorily in 
this way, there would certainly not be any corresponding 
association of mental characters, and no racial, mental, or moral 
superiority in any one. Obviously no strictly logical classi- 
fication of races of men is possible. And yet it is universally 
agreed that man has characteristics separating him off distinctly 
from ail other animals. Apparently, then, animal grouping is 
not altogether impossible. 

Boys do not hesitate to put into a single class all the known 
varieties of dogs, and to distinguish them clearly from cats, 
though they may not be able to say that the main specific 
differences between dogs and cats concern teeth and claws. 
Similarly they can distinguish between horses and asses, though 
they may not know that the main specific differences concern 
callosities and tails. The first thing for learners to understand 
in biological classification is specific differences, in order that 
they may obtain a clear idea of a species. 

But they must also learn that occasionally the amount of 



CLASSIFICATION AND TERMINOLOGY 187 

difference between parent and offspring is so strongly marked 
that the offspring may receive the name of variety; that it is 
often difficult to decide whether groups of similar forms should 
be ranked as species or as varieties, and that intermediate 
forms give rise to doubt; and that when a new animal is dis- 
covered, there is often a difficulty about coming to a decision 
concerning the species in which to place him, and that he may 
even have to be regarded as a member of a hitherto unknown 
species. 

The next thing for the learner to grasp is that the basis 
of specific differences is homological, not analogical. Homology 
expresses morphological, structural, architectural, develop- 
mental, similarities; analogy, merely the functional resemblance 
between the parts of different animals. Homologous structures 
reveal a deep-seated resemblance in build and in manner of 
development. Zoological classification seeks to show the blood- 
relationship of animals, because it is believed that all groups 
showing homological similarities really had, in some remote 
age, the same common ancestor, and such classification is 
therefore based on comparative anatomy, though much help 
is also obtained from embryology and palaeontology. Boys soon 
understand why whales must not be classed with fishes, or 
bats with birds. 

The biologist no longer believes in the fixity of a species. 
On the contrary, he believes that one form has given rise to 
another. The specific characters should exhibit a certain 
degree of constancy from one generation to another. No very 
great difference is likely to be seen in a hundred generations, 
or even in a thousand unless by special breeding. 

Explain to the pupils that biologists no longer attempt to 
define species by the method per genus et differ entiam, but by 
type. The difficulty of defining is due to the absence of clear- 
cut grouping. 

The next point for the teacher to take up is the various 
grades of classification, based on degrees of resemblance. The 
main principles are easily taught and always quickly under- 
stood, the successive groupings making a strong appeal to 

(E72) 14 



188 SCIENCE TEACHING 

boys. Thus species are grouped into genera, genera into 
families, and then into orders, classes, and phyla. Give one or 
two simple examples to be memorized, e.g.: 

Individual my dog Peter. 
Variety fox terrier. 

Species domestic dog (Canis familiar is). 
Genus Canis. 

Family Canidse (dog-like carnivora). 

Order Carnivora (flesh-eating mammals). 

Class Mammalia (vertebrates that suckle young). 
Phylum Vertebrata (animals with bony skeletons). 

Each main division is called a phylum, and includes animals 
built on the same fundamental plan and believed to be de- 
scended from one ancestral stock. 



Nomenclature 

One of the first things for pupils to learn is the biologist's 
recognized system of naming animals and plants. The name 
always consists of two parts: (i) the name of the genus (a 
capital initial letter is always used; (2) the name of the species, 
e.g. Canis familiarise Acer rubrum (the red maple). The name 
of a variety is added as a third name, e.g. Acer rubrum drum- 
mondii. These names are in universal use, and are found in 
the text-books of all the nations a great advantage. 

Classification in School Work 

Anything like a strictly logical and exhaustive classification 
of animals is quite outside the range of any course of zoology 
that may be taken in schools. But the main characteristics of 
the principal phyla should be familiar to a Sixth Form boy (the 
Protozoa, Porifera, Coelenterata, " Worms ", Echinodermata, 
Arthropoda, Mollusca, Vertebrata. Some knowledge of the 
five classes of the vertebrates (Fish, Amphibians, Reptiles, Birds, 
Mammals) should be given, and a few of the best-known 
orders and families of each of these five classes should be 



CLASSIFICATION AND TERMINOLOGY 189 

known, more especially those of the mammals. By the time 
a boy has completed his course of zoology, he should be able 
to assign any animal studied to its proper place in the zoo- 
logist's genealogical tree. He will then be able to take up 
evolution intelligently. But during the main course of zoological 
teaching, it is neither necessary nor desirable to introduce 
minutiae of classification. It would only serve to obscure things 
of much greater importance. Still, the principles of classifying 
should be understood. 

In botany, Sixth Form pupils should be familiar with the 
distinctive characteristics of the four great Phyla, and with those 
of the main divisions of the fourth: 

1. Thallophyta (algae, fungi, lichens). 

2. Bryophyta (mosses, liverworts). 

3. Pteridophyta (ferns and their allies). 

4. Spermaphyta, viz. 

(a) Gymnosperms (conifers, &c.). 

(b) Angiosperms, viz: 
(i) Monocotyledons. 

(ii) Dicotyledons. 

The principles underlying the classification of dicotyledons will 
generally have been taught in forms below the Sixth. It is 
quite enough even for Sixth Form pupils to be familiar with 
just a few " orders ". Do not waste time over unessentials. 

Biological Terminology 

This is always forbidding to a layman unless the layman 
knows something of Greek, and then he will grasp the inner 
significance of the meaning of a term more readily than the 
average biologist himself. To some biologists a biological 
term is just a label for tying on to a particular thing, and to 
him abracadabra would do just as well as prosenchyma. It is 
desirable that, from the first, teachers of biology should make 
their pupils hunt out from the dictionary the origin of every 
new biological term introduced. By a rational grouping of 
words, the memory is helped enormously: e.g. 



190 



SCIENCE TEACHING 



arthropod 
cephalopod 
gasteropod 
myriopod 


hydrozoa 
meta#oa 
polyzoa 
protozoa 


blastoderm 
ectoderm 
endoderm 
echinoderm 


biogenesis 
epigenesis 
pangenesis 
parthenogenesis 


arthropod 
arthroderm 
arthropterus 
arthrozoa 



and so generally. A hundred biological terms may hang upon 
less than a score of common Greek words (they are usually 
Greek), and, in nine cases out of ten, the term is derived from 
two Greek words, e.g. we have polyzoa, protozoa, protoplasm, 
ectoplasm, ectoderm, blastoderm, blastula, and so on, almost 
indefinitely. Some readers may be surprised if they make out 
a list of ordinary biological terms derived from these few very 
common Greeks words: cipOpov, ^8/09, /SXao-ros, /8/QiW, ya/xo9, 
ya<TT*//o, yeveari?, Sepju.a, e/croy, evSov, ^wov, OaXAoy, K<f>a\)'i, 
Troi'y (TTO^-), Tr/oclrroy, Trre/a/9, crTTe'p/za, cnropa, (rcS/xa, <f>v\\ov, 

<f)V\OV, <j)VTOV. 

There is a curious tendency to confuse phylon, phyllon, and 
phyton. 

Biological teachers should see that their pupils pronounce 
the terms properly. It is a common thing to hear wrong accen- 
tuation, e.g. the stressing of the penult instead of the ante- 
penult, as in parenchyma. 



CHAPTER XVI 

Botany 

Experiments Essential from the Outset 

A standard work in botany written by an English professor 
about thirty years ago devoted just three times as much space 
to plant classification as to plant physiology. It would not be 
altogether unjust to say that such a book made three times as 
great an appeal to the memory as to the intelligence. In teaching 
botany, experimentation must be given a foremost place. 

There is one great difference between school experiments 



BOTANY 191 

in botan^ and those in physics and chemistry, and that is that 
the former may extend over several days or even weeks. Evi- 
dently it is an advantage for several experiments to be in 
progress simultaneously. The pupils make periodical observa- 
tions of each, recording and dating these on separate pages of 
their note-books, for discussion later. A great deal of school 
time is often wasted because the experimental work in botany 
is badly organized. The fact that the problem of organizing 
courses in experimental botany has its special difficulties must 
be faced; the problem must be thought out. 

In justice to himself the botany teacher should remember 
that nearly all plant physiology experiments, even in the hands 
of expert botanists, are seldom more than partially successful; 
and that adequate evidence for the purpose of logical reasoning 
is often difficult to obtain. 

The Earlier Work in Botany 

The earlier work in botany, though simple, should aim at 
the experimental discovery of important general facts about 
plants; for instance, that the root absorbs water containing 
dissolved substances, and passes it up the stem; that the stem 
conducts such water from the roots to the leaves; that the 
leaves spread out into the light, and that water is evaporated 
from them; that all living plants need oxygen, just as animals 
do, and, like them, give off .CO 2 (never mind the reverse pro- 
cess in photosynthesis, at this early stage); and that the growth 
of the plant is promoted by warmth and moisture. The pupils 
will probably already have some knowledge of these things, 
but their vague knowledge must be converted into certain and 
exact knowledge. 

Telling work on such a subject as the germination of seeds 
may be done by quite young pupils, as we have already pointed 
out. The work is so important that we may refer to it again. 

Necessary directions for observation and experiment can 
be easily drafted, and most of the work left to the pupils. The 
usual box with a side of glass sloping inwardly, damp chopped 



192 SCIENCE TEACHING 

sphagnum and blotting-paper, a few small boxes of 1 different 
kinds of soil, are nearly all that is required. Each pupil makes 
daily observations and records. Some such scheme as the 
following would meet the case: 

1. Germinate seeds at different depths; other conditions to be 
the same. 

2. Germinate seeds at different temperatures (keep one box in 
a cold room, one in a room at normal temperature, one in a hothouse 
temperature); all other conditions to be the same. 

3. Germinate seeds under different conditions of moisture in 
dry soil, in moist soil, in saturated soil. (In the last, the roots may 
come up to the surface, to get air.) 

Three or four different kinds of seeds should be used for each 
of the above experiments. 

4. Note how the seed-coats burst in different seeds. 

5. Note how the embryos break out of the soil. 

6. Try to grow seeds in an airtight glass jar containing a little 
pyrogallic acid (place seeds on a moist sponge suspended to cork). 

7. Grow equal weights of mustard seed under exactly similar 
conditions, but one in light, and one in the dark. Dry, weigh, and 
compare the weights now. 

8. Observe the growth of the roots of seedlings. Mark with india- 
ink rings, i mm. apart. 

9. Observe the growth of the stem of seedlings, marking as before. 

10. Note direction of growth of root and stem. Place growing 
seedlings in horizontal and other positions, and find out what part 
of the root bends in turning downwards. 

11. Cut off the tips of some roots, and note what happens. 

12. Record amount of growth of root and of stem day by day. 

Of course such directions are not full enough for young 
pupils, and a teacher would have to elaborate them very con- 
siderably. The work might continue until the seedlings are 
well developed. The important thing is to vary one condition 
at a time. Good reasoning is then possible. 



Sixth Form Work 

Sixth Form work generally covers School Certificate work 
carried to a higher standard, and, in addition, such topics as 
the following: 



BOTANY 193 

1. S^me knowledge of the external morphology and the 
main anatomical features of a few common dicotyledonous 
trees and conifers. 

2. A certain amount of comparative morphology and biology. 

3. Tissue structure. 

4. Plant ecology. 

5. Flowerless plants. The structure, life history, and 
habitat of certain types, and especially the comparison of the 
different genera from the point of view of the differentiation of 
the plant-body, the different methods of sexual and asexual 
reproduction, and other aspects of plant evolution. 

(i) Flagellata Euglena. 

(ii) Algae Chlamydomona, Protococcus, Spirogyra, Vaucheria, 
Fucus. 

(iii) Fungi Agaricus, Mucor, Eurotium, Saccaromyces, Bacillus. 
(The part played by Fungi in plant disease.) 

(iv) Pteridophyta Lastrea (Aspidiwri), Selaginella, Lycopodinm. 

6. Plant physiology: some quantitative relations. 

7. Elementary considerations of evolution and genetics. 

The two main things are the plant physiology and the work 
with the microscope. Second-year Sixth Form pupils should be 
fairly proficient in their physiology experiments, and should 
have acquired reasonable skill in the use of the microscope. 

Pupils should be taught how and what they can learn from 
the microscope, and be made to understand that the microscope 
is not just a useful instrument for verifying other people's work. 
They should practise cutting transverse and longitudinal sec- 
tions until they can cut them well, and they must learn how to 
use the common reagents, and so gain a knowledge of the 
appearance and the reactions of the parts of the cell and of 
some of the bodies commonly contained in it the cell-wall, 
the protoplasm and nucleus, starch, chloroplasts, and so on. 

Naked-eye observation of a bulk of tissue easily handled 
should precede the work with the microscope. Take, for in- 
stance, five or six inches of the stem of a well-grown sunflower 
plant, cut a longitudinal section through a node, and dissect 



194 SCIENCE TEACHING 

out the course of the several vascular bundles; trace tfce course 
of the several bundles entering from the leaves. Get a first 
rough idea of plant structure in this way. (A good deal of 
work of this kind will, presumably, have been done in the 
middle Forms.) 

Now examine the vascular system of a young seedling of 
the sunflower by means of a succession of transverse sections, 
examined in proper order under the microscope. By comparing 
the sections, it is possible to reconstruct in the mind the whole 
shoot from which the sections were cut, and this is the impor- 
tant thing for the pupil to learn. He must not look upon a 
section as a mere network of cell walls, but as a slice of tissue 
which had a certain definite position in the plant from which it 
was cut. 

Let him now cut sections of two or three new stems or 
roots, and discover for himself the structure of the contained 
vascular systems. At first he will find it difficult to interpret 
the story that the different sections tell him, to visualize the 
whole of the internal structure of the plant. But a little practice 
will do much. When his eye has had the preliminary training, 
then and only then can he profitably begin systematic work 
with the microscope. 

A beginner's longitudinal (radial and tangential) sections 
are often cut obliquely, with the result that his reconstructed 
mental picture is hopelessly confused. 

Pupils' drawings of their own sections must be well 
executed. To be of any real value, these must be followed up 
by an intelligent interpretation. 

School Gardens 

One enterprising London school (the James Allen School 
for Girls) has been developing its gardens for over thirty years, 
and every botany teacher should see them. They originated 
in a few Order beds which included leguminosae and solanacese, 
for it was considered advisable, even in those early days, to 
make London acquainted with the growing of vegetables. Special 



BOTANY 195 

plots we^e arranged for pollination experiments and for photo- 
synthesis experiments. Flowers were left to form fruits, and 
various methods of seed dispersal were studied. As the school 
soil consisted of London clay, chalk soil was brought from 
Surrey, sea sand from Lowestoft, soil from salt marshes at 
Gravesend and Burnham-on-Crouch, all for the purpose of 
growing special types of plants. A heath was also planted; 
so was a wood which now contains several hundred trees; 
so was a lane 160 feet long, consisting of a grass walk 8 feet 
wide, bordered on either side by hedgerows and ditches. The 
school is now in possession of a heath 100 feet by 40 feet, a 
sand dune, a pond 34 feet by 23 feet; a salt marsh, two fresh- 
water marshes, a peat bog, and many other valuable features. 
The work of the gardens is designed to serve the purpose of 
making botany a real science. A large number of experiments 
are carried out, and a wealth of plants is available for the pur- 
pose. The botany is taught as it should be taught in the garden 
and in the laboratory. 

Few schools could compete with this particular school. 
Neither is it necessary for country schools to take so much 
trouble: woods, lanes, hedges, ponds, heaths, marshes, are 
often easily available. But in large towns school gardens are 
of the very greatest value. 

Such operations as grafting and budding may usefully be 
done in the school garden. But care must be taken not to allow 
the main subject, botany, to be overshadowed by horticulture. 
After all, gardening is not a science -yet. 

Rambles and Excursions 

These are not always successful, and sometimes they are 
wholly unprofitable. A few members of a party are usually 
interested, especially if the responsible teacher is a keen 
naturalist, but the majority tend to chat about trifles, perhaps 
pick a few flowers and probably throw them away at the end 
of the day. The work to be done on an excursion must be 
properly organized. Either the teacher must take the lead, 



196 SCIENCE TEACHING 

draw attention to the things to be observed, and see that notes 
and sketches are systematically made; or small batches of 
pupils should be told off to co-operate in doing certain types 
of work, it may be on the ripening of fruits, or on the dispersal 
of seeds, or on defences against the hot sun or frost. Things 
observed should be described, not merely named. It is a 
good plan to make the same excursion two or three times, at 
intervals, marking down plants of special interest to be examined 
and re-examined. In that way much may be learnt. 



By-ways in Botany 

If time could be found for them, all sorts of interesting 
topics might be included in a botany course, especially topics 
of economic interest. For instance, it is known that 10 per cent 
of the world's crops are lost annually through the depredation 
of insects, and a large percentage of the empire's crops are lost 
annually through the encroachment of noxious weeds. Thirty 
million acres in Australia are put out of action by the prickly 
pear, and huge areas of cultivable land in New Zealand are 
going under to the blackberry and bracken fern. To boys it 
is an unforgettable fact that in the south island of New Zea- 
land there is a current saying on the west coast that they have 
a blackberry bush 200 miles long. Facts like this stir up the 
boys' interest in economic entomology. The story of the 
successful world hunt for a plant-feeding insect that would 
eat up the prickly pear and not eat up anything else, and the 
present hunt for an insect that will feed exclusively on the 
blackberry, are stories to awaken interest in a new branch 
of knowledge of great economic importance. 

Another thing always interesting to pupils is poisonous 
plants. They like to know that cattle always avoid foxgloves 
and daffodils, apparently fearing them instinctively; and yet 
the cattle are not wise enough to avoid the meadow saffron or 
ragwort. The ignorance of children as to the harmful nature of 
common plants is profound the attractive-looking fruit of the 
deadly nightshade, the berries of the yew, the seeds of the 



BOTANY 197 

common'laburnum, the enticing seed-pods of Arum maculatum 
(" lords and ladies "), ivy berries, the " currants " of the 
common laurel, the pasque-flower, cow parsley. Then again, 
children should avoid handling the primrose called obconica y 
some daffodils, and some ivies. The caper spurge exudes an 
obnoxious milky sap. A list of poisonous plants should be 
given to all children learning botany. 

The Ministry of Agriculture issue a useful pamphlet, 
" Poisonous Plants on the Farm ". 



Final Snags 

i. CONTROL EXPERIMENTS. An experiment is often under- 
taken to discover the relation between some function of a 
plant and some particular external condition, and we try to 
observe the effect upon the plant when that condition is 
removed or neutralized. But different conditions are often so 
closely associated that the removal or neutralization of a single 
condition is difficult, perhaps not possible. To help make 
sure that the result obtained is really connected with the 
condition selected, and not with some secondary influence 
introduced by the manipulation in the experiment, it is usually 
necessary, and always advisable, to try at the same time a 
parallel experiment, in which a similar plant is placed under 
precisely the same external and experimental conditions as 
the first plant, except that the particular selected condition is 
not changed. Thus, in both experiments, all the conditions 
save one are the same; the difference is only in the particular 
selected condition. Hence it is a fair inference that an observed 
effect is connected with the change in the selected condition. 
Such a parallel experiment is called a " control ". The term 
is not a good one, though its intended meaning is clear. Such 
an experiment helps to check the accuracy of the facts from 
which we draw an inference, but it is a common thing to find 
children with a very hazy idea as to its purpose. 

A fruitful source of error in control experiments is due to 
the fact that no two plants are exactly alike and their behaviour 



198 SCIENCE TEACHING 

is probably never quite the same. Even in the same*plant no 
two parts are exactly alike, and the variation, no matter how 
small, may give rise to experimental differences which may 
lead to unsuspected errors. Hence, in control experiments, 
selected plants should not only be of the same stock, or at least 
as near akin as possible, but the two roots, or shoots, or leaves, 
should be from the same plant; or, better still, the leaves or 
other parts should be from the same shoot; or, still better, 
the two corresponding parts should be from the same leaf or 
other organ. In this way the possibility of error is reduced to 
a minimum. The difference in the age of the plants, and even of 
the parts of plants, is especially liable to introduce serious error. 

2. CULTURE SOLUTIONS. These fail more commonly than 
not. Success may reasonably be expected if the following pre- 
cautions are taken: (i) Guard against " damping off "; (2) 
darken the roots; (3) add water each day to replace that eva- 
porated; (4) once a month, take out the plants, wash the 
roots, place in plain water for two days, then in a fresh culture 
solution; (5) see that the solution is not alkaline; (6) force 
air into the solution daily. Here is a good culture solution: 
2 gm. of calcium nitrate, i gm. each of potassium nitrate, 
magnesium sulphate, and potassium phosphate, a drop or two 
of iron chloride, in 4 or 5 litres of distilled water. 

3. RESPIRATION. Loose reasoning and unsatisfactory ex- 
periments on respiration are common. For beginners, Pro- 
fessor Ganong's experiment is as good as any. His respiroscope 
consists of an inverted U-tube, one end being corked, the 
cork supporting a small wad of miost sphagnum on which 
rests, say, a few soaked oats, and the other end being open. 
Three such tubes are prepared. Three large test-tubes are 
also wanted, large enough for the open limbs of the U- tubes to 
slide in freely with a little room to spare. These test-tubes 
are half filled, one with a strong solution of caustic potash, 
one with a concentrated mixture of pyrogallic acid and caustic 
potash, and one with water. 



BOTANY 199 

The pupils must already have learnt that carbon dioxide is 
readily absorbed by caustic potash, and oxygen by a mixture of 
pyrogallic acid and caustic potash. 

The discussion that would follow the experimental results 
would probably take the following sequence: 

(1) The pyrogallic acid solution in a short time rises in the 
U-tube about one-fifth of its length, the oxygen being absorbed. 
The seeds do not germinate. 

(2) In the potash-tube the liquid rises to the same height, 
but more slowly; the seeds germinate, and grow considerably. 
The seeds absorb the oxygen and give off the carbon dioxide 
which is absorbed by the potash, and the potash rises to occupy 
the space left. 

(3) But this potash-tube result does not prove that anything 
is given off, since the rise of the liquid is accounted for by the 
removal of the oxygen. All that the experiment proves is that 
something is absorbed, doubtless oxygen from the air by the 
seeds. But the third tube helps us here: 

(4) In the water-tube, the seeds germinate and grow as 
in the potash-tube, but the water rises in the tube scarcely at 
all, showing that a gas is given off as w r ell as absorbed; and 
since the only gas absorbed by potash is carbon dioxide, that 
gas must be given off in volume equal to the oxygen absorbed. 

Thus pupils learn from the experiment that oxygen seems 
to be necessary to growth, that carbon dioxide seems to be 
given off during growth, and that the volumes of gas thus 
exchanged are equal. 

(It is a good plan to show in a preliminary experiment that 
germinating seeds really give off carbon dioxide, by placing 
in a closed bottle a number of soaked seeds with a small dish 
of clear lime-water. After two or three days the turbidity of 
the lime-water indicates the presence of carbon dioxide.) 

Germinating seeds are selected instead of a green plant in 
order that the experiment may not be complicated by the 
opposition and reverse process of exchange of oxygen and carbon 
dioxide in photosynthesis. 

Of course the whole experiment is of a very rough and 



200 SCIENCE TEACHING 

ready kind, and, for advanced pupils, various refinements are 
necessary. As a quantitative experiment, it is of little value, 
if only because the rise of the liquids in the tubes cannot 
possibly mark the extent of the absorption. Allowance has 
to be made for pressure and temperature differences, and the 
gases have to be tested. In short, a crude respiroscope cannot 
be used as a respirometer. 

But the beginner does learn from the experiment the 
essential thing about plant respiration. And the close analogy 
with animal respiration should always be pointed out. 

4. PHOTOSYNTHESIS. It is assumed that pupils have already 
learnt from the usual experiments that, for photosynthesis to 
proceed, carbon dioxide, water, light, and chlorophyll are all 
essential; that he knows that carbon dioxide and water are 
the initial products, and sugar and starch the final products. 
The real trouble now begins. 

The " photosynthetic equation ", viz. 

6C0 2 + 6H 2 - C 6 H 12 6 + 60 2 , 

may be allowed to stand, but the intermediate equation, show- 
ing, first, the formation of formaldehyde from CO 2 and H 2 O, 
and secondly, the formation of sugar from formaldehyde, must 
be given as mere possibilities. It is dangerous to enunciate any 
sort of final dogma concerning photosynthesis; the subject is 
still controversial. 

The pupils should be made to realize the far-reaching im- 
portance of this process of photosynthesis. The green plant 
is the basis of the food supply of all living animals, including 
man, because of its remarkable power of building up, in the 
presence of sunlight, sugar from water and the carbon dioxide 
of the air. The sugars and the other carbohydrates formed from 
them are reservoirs of energy which, in the form of food, enable 
animals to do work. But the chemical and physical details of 
the photosynthetic process are not fully known. 

Formaldehyde is actually found in green leaves, and has 



BOTANY 201 

long bee$ considered to be an intermediate photosynthetic 
product. Hence when the late Benjamin Moore succeeded in 
synthesizing formaldehyde from CO 2 and OH 2 , using for the 
purpose the energy of light, the assumption that the same 
process took place in the green leaf seemed to be confirmed. 
A few years later, Professor Baly succeeded in the next step, 
viz. in converting formaldehyde into sugar, using the energy 
of ultra-violet light. 

But Professor Baly has since demonstrated that CO 2 (with 
OIL) may be converted directly into sugar, O being given off 
during the process, formaldehyde not forming a stage in the 
synthesis. Then what is the origin of the formaldehyde in the 
leaf? Is it an intermediate synthetic product, or is it a mere 
by-product due to the disintegration of carbohydrates already 
formed? We do not know, and pupils must be told this.* 

Warn the pupils of the danger of drawing illegitimate 
inferences from the achievement of organic photosynthesis in 
the laboratory. It does not at all follow that, because we have 
succeeded in manufacturing thousands of organic compounds, 
we shall ever succeed in making a living thing. A plant or 
animal that has just been killed contains, presumably, just the 
same organic compounds as before, but we do not know how 
to make these compounds " live " again. When once a func- 
tioning green leaf has been put together artificially, then indeed 
will a miracle have been worked. 

Impress pupils with the need of being very cautious in 
arguing about these things, on the ground that our knowledge 
of them is only slight. 

5. THE TRANSPIRATION CURRENT. It is assumed that the 
pupil knows something about diffusion and osmosis, and some- 
thing about the entrance of water into tissues despite increasing 
hydrostatic pressure; that he has learnt how the stem is a 
means of communication between root and leaves and that 
he can visualize the communicating channels; that he has 

* Professor Baly's most recent researches into photosynthesis are summarized 
in a Royal Institution Discourse which he delivered on Feb. 3, 1928. 



202 SCIENCE TEACHING 

learnt that only a small portion of the water absorbf d by the 
root-hairs is absorbed osmotically by neighbouring cells, and 
that by far the larger part travels as a current from root to 
leaves where it is transpired; that he has learnt that this trans- 
piration current does not break, no matter how rapid the trans- 
piration, and that, if the current ceases to flow, transpiration 
stops. Then the pupil ought to have no difficulty in under- 
standing that since the current does not break, and since it 
may rise to the top of the tallest trees (say 300 feet), there must 
be a great force at work to push it up. 

The root-pressure resulting from the osmotic absorption 
of water is wholly inadequate as an explanation, especially as 
root-pressure cannot be detected in many plants, and in none 
when transpiration is active. How, then, is the upw r ard moving 
current of water to be explained? 

One common experiment is to soak a piece of parchment 
membrane in water and tie it tightly over the wide end of a 
thistle funnel, to fill the funnel completely with boiled and 
cooled (and therefore air-free) water, to close the narrow open 
end with the finger, and, holding the tube thistle-end upwards, 
to plunge the open end in a basin of mercury. Of course water 
gradually evaporates from the parchment surface and the 
mercury rises up the tube. The explanation sometimes gravely 
put forward is that the parchment surface is like the transpiring 
leaf surface, and that the mercury is " lifted " or " pulled 
up " the thistle funnel tube in exactly the same way as the 
transpiration current is lifted or pulled up the tree. Both, 
so it is said, are the simple result of the evaporation of the 
water. 

The explanation is just as absurd as Herodotus's explanation 
of the Nile floods that they were due to the sun " drawing " 
the water. 

Even a Third Form boy ought to see at once that the 
mercury rises in the tube because of the outside atmospheric 
pressure; the atmospheric pressure is able thus to show itself 
because of the diminishing water pressure. If the experiment 
is done in a vacuum, or, better still, if the tube used in the 



BOTANY 203 

open excteds 33 or 34 inches in length, the experiment fails; 
or rather the experiment shows conclusively that the limited 
rise of the mercury was due exclusively to atmospheric pressure. 
It throws no light whatever on the rise of a transpiration 
current. 

If no tree exceeded the height of about 34 feet, the inference 
that the rise of the current is due to atmospheric pressure would 
perhaps be justifiable from the facts known. That we now 
know the inference to be wrong serves to show how, in the 
absence of sufficient evidence, an explanation may be entirely 
misleading. 

No hypothesis yet put forward in explanation of the rise 
of the transpiration current is quite satisfactory. Not one 
squares with all the known facts. 1 * 

We do not know, and this the pupil must be told frankly. 

It is this baffling nature of many of the processes of plant 
physiology that makes some competent authorities doubt 
whether botany is a suitable subject of science for schools. 
As a subject for purposes of observation, it stands perhaps first; 
as a subject for experiment, it is full of very serious difficulties. 
Experiments are rarely quite satisfactory, and inferences from 
them are often seriously inaccurate, even when the rules of 
logic are carefully observed. 

Dr. Wager, F.R.S., is the chief authority on botany teaching 
in this country, and his remarkably lucid way of putting things 
will be familiar to all teachers who have read his articles in the 
successive editions of the Encyclopedia Britannica. Teachers 
of botany who find themselves in difficulties over particular 
points should consult him, and those who are able to attend one 
of his summer courses for teachers should certainly do so. 

* In Nature for Aug. 4, 1928, there is an interesting letter from Professor 
Molisch of Vienna, describing experiments on sap movement, as designed by Sir 
J. C. Bose. The results seem to show conclusively that the movement is not due 
either to a root-pressure push from below or to " suction from above " by trans- 
piring leaves. There seems to be an inherent activity in the stem itself independent 
of the activities in the terminal organs. The movement seems to be less strictly 
physical than physiological, the flow apparently being pulsatory; the pulsation may 
be markedly increased by certain stimulants. 

(E72) 15 



204 SCIENCE TEACHING 

CHAPTER XVII 

Zoology 

Function rather than Form 

For the teacher of zoology, there is now available a wealth 
of admirable text-books w r ritten in consonance with the accepted 
principles of present-day treatment of the subject. In the older 
books the usual plan was to devote a chapter to some animal 
selected as representative of its group (species, order, class, as 
the case might be), and to make the study of it mainly morpho- 
logical. Differences between one animal and another were 
stressed, but fundamental resemblances were only lightly dealt 
with. Thus the teaching followed on much the same lines as 
the teaching of botany. Morphology received chief attention, 
function but little. 

Just as plant physiology is now taking the leading place in 
the teaching of botany, so it is with animal physiology in the 
teaching of zoology. There are certain phenomena charac- 
teristic of all living animals growth, reproduction, locomotion, 
nutrition, respiration, excretion, response to environment; and 
in any scheme of instruction it is those phenomena that must 
be given a foremost place, and each be studied comparatively. 

There are two text-books on zoology that all teachers of 
the subject should read, Professor J. Arthur Thomson's and 
Professor Dakin's. 

The first eighty-seven pages of Professor Thomson's book 
are devoted, first, to a general survey of the animal kingdom, 
then to elementary considerations of physiology, morphology, 
embryology, palaeontology, and the doctrine of descent. Then 
follows (pp. 88-836) a systematic study of the whole animal 
kingdom, phylum by phylum. 

The chapter on physiology, dealing with the life-activity 
and function of animals, considers briefly, but very lucidly, 



ZOOLOGY 205 

such topits as nervous activity, muscular activity, digestion, 
absorption, respiration, and excretion. The resemblances and 
differences between animals and plants, as regards both struc- 
ture, function, and development, are happily summarized. The 
chapter on morphology deals adequately with symmetry and 
homology; and that on palaeontology, with the imperfection of 
the geological record and with the extinction of types. Alto- 
gether, these eight-seven pages are a really excellent intro- 
duction to the whole subject. And in the next 748 pages a 
teacher will find ready to hand all the material he needs for 
studying selected types. Professor Thomson is recognized 
as a born teacher as well as a front-rank naturalist. 

Professor Dakin makes a rather new departure. His book 
is a complete justification of the right of zoology to be con- 
sidered as a suitable experimental subject for school work, 
and it is certainly an excellent guide to the teacher as to the 
way in which the relative claims of function and structure 
may be adequately met. Function is the dominating note of 
the book, and, except for a chapter on the protozoa, the subject- 
matter is arranged under the headings of the various functions 
of animals, and not under the customary systematic groups. 
In dealing with any one function, the author gives just so much 
structural detail of the organs concerned as is necessary for a 
comprehension of their uses. The book is full of excellent 
suggestions for experimental work, especially experiments for 
practical demonstrations of the physiological processes under- 
lying function. 

In the study of multicellular animals (Metazoa), the author 
shows clearly how, with the increase of structural complexity, 
there is a corresponding specialization of parts of the body; 
how, for instance, as we ascend the animal scale, a special 
digestive tube running through the animal is developed, ;:nd 
how this necessitates a circulatory system to convey the digested 
food products to all parts and to carry away waste products; 
further, how special areas are gradually developed for respira- 
tion, and special structures for excretion and reproduction; 
also, how this increasing differentiation then demands a co- 



206 SCIENCE TEACHING 

ordinating system, with the result that a nervous system with 
controlling centres and sense organs appears, putting every- 
thing into touch with the environment. All this is worked out 
in a way that makes a strong appeal to the reasoning powers; 
and the animal types selected and the experiments proposed 
are exactly what the teacher needs for making a series of 
studies in comparative morphology and comparative physio- 
logy. 

In the section on nutrition, for instance, the food and diges- 
tion of the following animals are considered: sheep, frog, fish, 
crayfish, cockroach, bee, housefly, ascaris, hydra. Other topics 
similarly considered are, respiration and respiratory organs, 
transportation systems, the blood, temperature and animal life, 
the animal skeleton, animal movements, cells and tissues, the 
nervous systems and the sense organs, growth and reproduction, 
life histories, evolution and heredity. In each case the most 
suitable animals, from lower to higher, are selected, and the 
increasing functional complexities worked out. Under each 
topic, a large variety of useful experiments for practical work 
are suggested. 

Many text-books on zoology give useful practical hints for 
laboratory work but Professor Dakin's hints are particularly 
valuable, especially for work with the microscope, e.g. fixing, 
dehydrating, embedding, section-cutting, treatment of sections 
after cutting, staining, and so on. His instructions for dis- 
section and practical work on common animal types the 
earthworm, butterfly, water-beetle, snail, mussel, crayfish, dog- 
fish, frog, rabbit are full of just those practical tips that the 
elementary student requires. The instructions direct attention 
to essentials, and do not distract it by unnecessary minutiae. 

Professor Dakin also gives useful warnings concerning the 
study of cell-structures, pointing out that what we see under the 
microscope are usually dead cells, and that some of the things 
we see may not have existed at all in the living cell. By killing 
the cell and staining it, it is of course possible to differentiate 
structures which cannot usually be seen in the living cell, 
the nucleus having a marked affinity for dyestuffs. It is only 



ZOOLOGY 207 

by careful comparison of the results of different methods of 
treatment, checked when possible by observations on those 
living cells which happen to allow of certain structures being 
very favourably seen, that we can be fairly certain of what is 
natural and what is artificial in what we examine under the 
microscope. 

Early Observational Work 

Is it best to begin zoology by considering a Protozoan or 
a Vertebrate? This is a very old question. And it is a very 
" nice " question. Do we gain by working upwards from 
simplicity to complexity, or by first giving details of a complex 
picture and working downwards to simplicity? 

On balance, the arguments seem to be in favour of begin- 
ning with a fairly thorough study of a relatively complex 
animal, say the frog or the rabbit. The subsequent sequence 
probably matters little, but most teachers will probably prefer 
to begin again, this time with a Protozoan and then to work 
systematically upwards. 

But before attempting to dissect (say) the frog, observations 
of the live animal should be made, and it is this kind of work 
that is so suitable for beginners. For instance: 

1. Watch the frog sitting. Note the fore and hind legs. 
Make the animal jump, and note the way the legs are used in 
jumping and in landing. 

2. Place him in a tank of water and note his movements, 
especially the use of the webs and the hind limbs. How long 
does he stay under water? Note his floating attitude if the 
water is too deep for him to sit on the bottom of the tank. 

3. Note his respiratory movements. Try to find out if he 
can see, feel, or hear. 

4. Turn the frog over on his back and note his movements 
while he is righting himself. 

5. Observe his behaviour during feeding. Place him in a 
covered dish with a little water, and add some live insects. 
From his behaviour, do you think that the frog sees, hears, 



208 SCIENCE TEACHING 

or smells the food? Observe the action of the tongue iifcapturing 
the food. 

6. Describe the feel of the frog's skin. 

7. Kill the frog with chloroform. Describe the head, 
trunk, and the two pairs of limbs. Note the absence of neck 
and tail. Describe the nostrils, eyes, the three eyelids, the 
tympanic membrane posterior to the eye, the mouth opening, 
and the jaws. 

Even when an Upper Form pupil begins the study of a 
new animal, he should begin, whenever possible, by studying it 
alive. As an example of a carefully thought out scheme, we 
give Miss Hymans's directions for examining a live crayfish. 

1 . Observe the animal's method of walking. Which append- 
ages are used? How are the others held? Can the animal walk 
sideways or backwards? Make the animal swim. What is the 
chief swimming movement? Explain the action of the muscles 
of the abdomen in swimming. Are the pleopods used in 
swimming? are they kept in motion when not swimming? 

2. Observe in a quiet specimen the continued rhythmic 
movement in certain appendages. Determine which appen- 
dages are concerned. (These movements are of a respiratory 
nature.) With a dropper, place a few drops of carmine sus- 
pension near the posterior edge of the bronchial region of the 
carapace. By the movements of the granules, determine if 
there are any respiratory currents and in what direction they 

go. 

3. With a glass rod drawn out to a blunt point, touch 
various parts of the animal and note response. Touch various 
appendages. Is the response different according to the part 
touched? Are some regions or appendages more sensitive than 
others? 

4. Drop a piece of fresh raw meat four or five inches from 
a crayfish. How long before the animal perceives the presence 
of food? Note its behaviour, and observe the method by which 
it finds the food. Observe the process of chewing the food,, 
and the use of the various mouth appendages in the process. 



ZOOLOGY 209 

Directions of this kind supplied to pupils are almost 
indispensable. By means of them, the pupils know exactly 
what to look for and how to set to work systematically. The 
directions should not tell more than is absolutely necessary, 
or the work may become mere verification of an almost pur- 
poseless kind. 

The following directions are, on this ground, open to 
criticism and they require to be redrafted. They tell the 
observer far too much, and yet the inquiry, if prope r ly directed, 
is exactly what is wanted. The examination is systematic and 
exhaustive. 

THE EXTERNAL ANATOMY OF THE WASP. Kill several wasps 
without mutilating them and mount them in different positions 
on fine needles thrust into corks. Examine with a hand lens. 

1. Observe size, shape, colour, and general anatomy. Body 
bilaterally symmetrical; dorsal and ventral sides alike, forward 
and hinder ends unlike, Legs on ventral side, wings on dorsal 
side. 

2. External surface smooth. Animal encased in a hard 
shell called the cuticula which is composed of chitin; it is the 
skeleton of the animal. 

3. Body composed of a number of serially arranged seg- 
ments. These are the somites or metameres. The body is 
sharply divided into three divisions, head, thorax, and abdomen. 

4. Head, unsegmented. Bears on its anterior and dorsal 
surface a pair of long jointed feelers or antennce (important sense 
organs), a pair of large compound eyes, and three small dot- 
like eyes called ocelli. On the ventral side are the mouth parts, 
the organs which taste, grasp, and masticate the food. Note 
the short overhanging upper lip, beneath which is a pair of 
powerful jaws having a lateral or side position. Beneath the 
jaws are the maxillae and under lip. Note the two pairs of 
elongated and segmented palps (probably organs of taste). 

5. Thorax, composed of three somites. Each somite bears a 
pair of legs on its ventral surface, and the two back somites 
each a pair of wings on the dorsal surface. Thus the organs 



210 SCIENCE TEACHING 

of locomotion are concentrated in the thorax. Find th*> sutures 
between the thoracic segments. The three segments may be 
difficult to distinguish at first, but each bears a pair of legs. 

6. Abdomen. No appendages. At the hinder end is the 
anus and in the female the sting. The dorsal and ventral por- 
tions of the cuticula are composed each of a distinct plate in 
each somite. 

7. Spiracles: the external openings of the respiratory system. 
They appear in a straight row of minute dots on each side of 
the abdomen and thorax, one dot being on each segment on 
each side. It is sometimes difficult to see them with a hand 
lens. In that case, remove a portion of the cuticula from the 
side of the body, and examine the inner surface with the 
microscope. 

8. Draw the body X 5, and the face separately X 10. 

9. Remove a leg from the hindmost somite and draw it 
X 5. The coxa is the segment articulating the leg with the 
body; the trochanter is a very small segment, the femur a long 
segment; the tibia or shank is also long; the tarsus or foot is 
composed of five small segments, the last one bearing two 
claws. 

10. Remove a forward wing, and draw it X 5, showing 
venation. 

Every opportunity should be taken of comparing animals 
of the same main group, and noting structural differences. 
For instance, with the wasp might be compared a bee, a large 
beetle, a blue-bottle fly, and a grasshopper, all easily procurable, 
and the following points might be noted. 

Beetle. The hard and thick forward wings are not used for 
flight, but are an additional protection for the back (they are 
called elytra or wing-cases); lift them and note how the wings 
proper are folded, transversely as well as longitudinally; the 
wings are wanting in some of the running beetles. 

Blue-bottle Fly. Note the hairy body; small antennae with 
pinnate terminals; extend the proboscis and note oral lobes at 
lower end; the big thoracic somite bears the wings; the hind- 



ZOOLOGY 211 

most thoracic somite bears the balancers, the morphological 
equivalents of the second pair of wings. 

Grasshopper. Pass a needle under the broad long upper 
lip and note the mandible] no separating constriction between 
thorax and abdomen; anterior wings are parchment-like and 
non-flying; proper wings folded up under them, like a fan. 

But in drafting directions for comparative studies, draft 
them in such a way as to compel the observer to discover 
things for himself. For instance, instead of saying, " lift the 
elytra and note how the wings are folded transversely as well 
as longitudinally ", say, " lift the elytra and note the wings; 
extend a wing as if for flying, and then try to put it back as 
you found it; how does the insect probably get the wing 
back? observe the unextended second wing and describe it 
accurately ". 

Further Work 

Comparison is the very essence of all zoological study, 
whether morphology or physiology is under consideration. It 
is excellent practice for pupils to make diagrammatic cross- 
sections of animals studied, consistently colouring in the same 
way the various organs and tissues of each. A succession of 
diagrams of this kind, showing the gradation from lower to 
higher types of animals, always serves to impress the learner 
with clear notions of evolutionary development. 

When dissection is undertaken, its main purpose should 
not be the study of morphological minutiae but the study of 
comparative function. Let function be given a place at least 
equal to that of structure. And always bear in mind that the 
main purpose of all the work done is to trace developmental 
paths from lower to higher types, from the protozoan to the 
mammal. This idea of development the learner must get into 
his very bones. 

Professor Thomson's, Professor Dakin's, and Miss Hy- 
mans's books (to mention only three) are so full of teaching 



212 SCIENCE TEACHING 

hints of all kinds, both as to selection of types and a$ to treat- 
ment in the laboratory, that it is unnecessary to give further 
details here. All the advice required for teaching zoology in 
Upper Forms is given in those books. 

For laboratory work, it is best to concentrate on a feu- 
principal animal types, the animals selected being easily pro- 
curable, easily handled, and telling their own stories most 
readily. The following is a suitable list: Amoeba (as an example 
of a less complex protozoan), Paramecium (a more complex 
protozoan), Hydra (a simple metazoan), then Planaria, Earth- 
worm, Starfish, Snail, Crayfish, Ike, Amphioxus, Dog-fish, 
Frog, Pigeon, and Rabbit. One lesson each is enough for half 
of these, and the whole can be done in about twenty two-hour 
lessons. But of course there is practical work of other kinds 
to be done as well, e.g. the life histories of the butterfly, silk- 
worm, moth, and frog, in addition to work suggested in the 
next chapters. 

Laboratory Procedure. The Microscope 

Always insist on the details of accepted laboratory pro- 
cedure being rigorously followed under-water dissection when 
possible, oblique fixing of pins, frequent changing of water, 
caution in cutting away tissues, keeping slightly on the stretch 
the parts under dissection, dissecting along and not across 
blood-vessels and nerves for cleaning, keeping all instruments 
clean and sharp, using clean droppers when handling small 
organisms, dropping cover-glasses on to a slide in such a way 
as to avoid air-bubbles. It is well to get out a list of all such 
rules of procedure, and make the pupils copy it on the first 
page of their note-books. Observance of such rules makes 
all the difference between success and failure in practical 
zoology. 

Specific instruction in the proper use of the microscope is 
too rarely given, and the result is that only a small minority 
of pupils learn to get the best out of the instrument. 

There should be one way and only one way of adjusting 



ZOOLOGY 213 

the inst?ument, to be followed by all pupils. It is preferable 
to teach beginners to focus by racking back; racking down 
frequently leads to damage. Most beginners use two much 
light, with consequent loss of definition. The condenser is 
seldom wanted in school work, and of course is never necessary 
for lower powers, good enough light then being obtainable from 
the concave mirror. With more advanced pupils using higher 
powers, a condenser (with the plane mirror) is useful. A T V-inch 
oil immersion should be kept in the teacher's cupboard, for 
the use of that occasional Sixth Form pupil who shows a flair 
for microscopy. 

Train the pupil not to use a greater power than that really 
required by the object, never to close the left eye, never to use 
the fine adjustment for powers less than J inch. The pupil's 
eye needs educating, and a beginner nearly always makes 
the mistake of using higher magnification than is necessary. 

The beginner must also be taught that as much depends on 
correct illumination as on lenses. Let him take out the eye- 
piece and look at the back lens of the objective; it is probably 
filled with light. He should then close the iris down until 
about three-quarters of the lens is filled. This is about the 
best for a good definition. 

Further, the pupils must learn that the plane of the focus 
of a lens is merely a geometrical plane. Since all objects viewed 
through a microscope have an appreciable thickness, not even 
the thinnest can be seen in its totality in a single plane of 
focus. Hence the pupil must be taught that, when viewing, 
he must vary the focus and so bring it into different planes. 

The pupil should not only label all his sections consistently, 
but should note down the magnifications consistently. If an 
objective of -inch focus forms its image at 10 inches, it gives 
at the distance a magnification of 40. If the magnification of 
the ocular is 10, the magnifying power will then be 40 X 10 
or 400 (diameters). Most modern objectives are corrected to 
a tube length of either 6 to 8 inches, or 8 to 10 inches. The 
facts should be obtained from the makers, and the details posted 
up on the inside of the door of the case of each microscope. 



214 SCIENCE TEACHING 

Collections of Animals 

London schools have a tremendous advantage in having at 
their doors the Zoological Gardens and the Natural History 
Museum. The special exhibits in the Central Hall and in the 
North Hall of the museum are highly instructive and should 
be seen by every zoology student. For instance, not far from 
the elephants is a case showing the damage caused by wood- 
wasps and their allies; the damage is remarkable. In the 
mimicry case is a recent addition showing mimicry in beetles. 
Then there is a number of skeletons of famous race-horses, 
and the visitor is able to compare the result of premature 
strain on the backbone of a horse raced as a two-year-old, with 
the normal backbone of the famous Eclipse who did not run 
until he was five years old. In short, there are to be seen all 
sorts of things full of interest to a naturalist; and a knowledge 
can be acquired that is an entirely different sort of knowledge 
from that obtained in laboratory courses, and even different 
from that obtainable from ordinary text-books. And of course 
the first-hand animal knowledge to be obtained at the Zoological 
Gardens is almost unlimited. The new Aquarium there is said 
to be the best in the world. A similar claim is also made for 
the new Reptile House. 



MORE USEFUL BOOKS 

Borradaile's Manual of Elementary Zoology, Lulham's Introduction 
to Zoology, Bourne's Introduction to the Comparative Anatomy of 
Animals, Mr. Latter's Elementary Zoology (full of teaching sugges- 
tions), Lankester's Zoology (eight parts), Marshall and Hurst's Prac- 
tical Zoology (an old friend still very useful) all should be in the 
Teacher's Reference Library. Huxley's Crayfish and Marshall's 
Frog, written long ago, are still models of their kind. 



HUMAN PHYSIOLOGY 215 

CHAPTER XVIII 

Human Physiology 

To what Extent is the Subject Necessary? 

If the school biological course includes the study of zoology, 
and if zoology has been properly taught, the essentials of 
physiology in the more general sense will have been mastered, 
and there will be little need to devote much attention to human 
physiology as such. If, on the other hand, zoology has not 
been included, and the pupil is introduced to the study of 
physiology exclusively from the point of view of the human 
body, serious difficulties are bound to arise. Any practical 
work attempted will, after all, be necessarily mainly work on 
the lower animals, and this, for the new purpose, can hardly 
be made zoologically systematic. 

The courses of practical physiology I saw in schools thirty 
years ago were generally based on Halliburton's Essentials of 
Chemical Physiology. Naturally the book was much too diffi- 
cult, the pupils' knowledge of chemistry usually being elemen- 
tary; but, more than that, the book was inappropriate, for it 
touched only one corner of a very big subject, and it failed to 
provide the type of experimental facts required for establishing 
the principles underlying the so-called " theoretical " course 
which ran concurrently with the laboratory work. The "theory" 
dealt mainly with anatomy and histology, function being 
treated, when treated at all, in a very perfunctory sort of fashion. 
It is very doubtful, too, if such modern text-books on practical 
physiology as that typified by Sir E. S. Shafer's work is suit- 
able for schools. The electrical apparatus now in common use 
for such physiological work is not available in schools, and the 
usual muscle-nerve preparations, and the nerve-conduction 
experiments, of the medical schools, hardly come within the 
range of work that ordinary school boys can best do. 



216 SCIENCE TEACHING 

It is interesting to compare Professor M. Foster's standard 
work on physiology, first published in the seventies, with the 
most recent edition of Professor Starling's work. It will be 
seen how anatomy tends to take a smaller and smaller place 
(it is, of course, provided elsewhere for the medical students), 
and physiology proper to occupy the premier position. 

Assuming that essentials have already been taught through 
the medium of the zoology course, there are still certain addi- 
tions which are necessary if pupils are to understand intelli- 
gently the working of their own bodily machine. A beginning 
might be made by reading Hill's Living Machinery , an excellent 
general book to rouse boys' interest in physiology. Then: 



Topics for Special Consideration 

i. THE HEART. It is assumed that an elementary study of 
the beating frog-heart has been made. 

(i) The Heart-beat. Rate of beat in the human subject. 
Place a finger either on the heart-apex or on an artery 
(pulse). Do this with the subject recumbent, sitting 
up, standing up, and after a hard run. Note the 
differences in the rate and in the character of the 
beat. 

(ii) Elasticity of Arteries. At each beat, about -J- pint of 
blood is forced suddenly into the aorta; there is a 
consequent arterial expansion and a pulse of pressure 
throughout the arterial system. The cycle of the 
heart. Place one finger over the carotid, and another 
over the artery at the wrist; the pulse at the former 
can be detected slightly before that at the latter. 
Evidently if we can measure this interval (as we can), 
and measure the distance from neck to wrist, we can 
estimate the speed of the wave. The pulse is not a 
flow of blood, but a wave of pressure. It runs much 
faster than the blood itself. The sphygmograph and 
its use. 



HUMAN PHYSIOLOGY 217 

(iii) Blood-pressure. The medical practioner's sphygmo- 
meter (rubber cuff and mercury manometer) and the 
story it tells: when the applied pressure is high 
enough, the arteries are squeezed flat, and the pul- 
sation of the heart ceases to go through to the lower 
part of the arm; how the pressure is recorded by the 
manometer. 

(iv) The Work of the Heart. -Every second the heart dis- 
charges blood from its cavities with a force equal to 
the lifting of a weight of from 10 to 15 Ib. Why does 
it not tire as other muscles tire? (This question may 
provoke an interesting discussion.) 

(v) Capillary Circulation. Microscopic observations of the 
circulation in the web of a frog's foot, or in a tadpole's 
tail. 

2. THE LUNGS. Respiratory movements; observations and 
records. Self-measurement of chest at deepest inspiration and 
expiration. Artificial respiration: practise on a recumbent 
subject. 

3. THE SKIN. Cutaneous sensation: determination of pain 
spots, warmth spots, cold spots, delicacy of different parts to 
touch. 

4. THE EYE. Co-ordinated movements of the eye; the 
optical vsystem of the eye; mechanism of accommodation; 
normal and abnormal refraction of the eye; binocular vision. 
Theories of vision. (See p. 146.) 

5. THE EAR/ Nothing very useful can be done unless the 
pupil has an elementary knowledge of sound. (See p. 143.) 

6. BIO-CHEMISTRY. We deal with this in the next section. 
Then there are various things in physiology that all the 

world are interested in and keen to know something of, things 
which, although they cannot be included within the scope of 
formal science teaching, may receive informal attention for a 
few minutes on appropriate occasions during particular lessons. 
One such thing is the process of muscular and tissue repair 
after injury or operation. The late Sir James Paget's description 



218 SCIENCE TEACHING 

of the reparatory processes that took place in a rabbitfs severed 
tendon, the separated pieces being nearly an inch apart, always 
makes a great impression on boys, especially the fact that, after 
the repairing process had gone on for ten days, it took a half- 
hundredweight to break again the newly connected tendon. 
(This test was made by removing the tendon from the dead 
body and slinging weights to it.) The repairs effected by nature 
are nearly always thorough. 

Another interesting thing is nerve regeneration. This pro- 
cess though slow is even more wonderful than the other. If 
a nerve-trunk be cut, the nerve-fibres from the point of sever- 
ance to the muscle or skin die along the whole length. But 
the other end, that in connexion with the brain, suddenly 
begins to grow (it may be after many years of quiescence!), 
and once more creeps along towards its proper goal, always 
ignoring alien tissues, until, threading through all obstacles, 
it reaches its goal and restores the broken function. Such 
an interesting fact as this might certainly be introduced into a 
lesson on the nervous system, whether the lesson was one on 
zoological development or one in the separate department of 
human physiology. 

There remains the difficult subject of bio-chemistry. 

Bio -chemistry 

Not the least important thing in teaching physiology is to 
tell pupils frankly that our knowledge of the subject is very 
far from being complete. Pupils should learn that the human 
body is a combined physical, chemical, and biological laboratory, 
the physical and chemical sections being fairly well understood, 
the biological scarcely at all. We reduce our physiology to 
physical and chemical processes, and these as physical and 
chemical processes w r e understand more or less; but how 
these processes are initiated, how enzymes act, how hormones 
act, how vitamins act, how an animal wills, all these and a 
score of other things are simply baffling mysteries, and nobody 
has ever succeeded in devising experiments to explain them. 



HUMAN PHYSIOLOGY 219 

Until* pupils have had a fairly good training in chemistry, 
including elementary organic chemistry, it is of little use for 
them to take up bio-chemistry. The subject is too difficult. 
The main source of difficulty is the extreme complexity of 
proteins; and all the phenomena which we term " life " are 
manifested by matter which is made up to a very large extent 
of proteins. All the other substances starches, sugars, fats, 
salts, and the rest- are really of secondary importance, materials 
waiting to be used by the living structure, rather than funda- 
mental parts of that structure itself. 

Even well-prepared pupils will not be able to take up more 
than the outlines of bio-chemistry. The subject has become a 
big one. 

The main difficulty underlying the investigation of proteins 
is their extreme liability to change. If a solution of protein 
be heated only a comparatively few degrees above the normal 
temperature of the body, irreversible processes of decom- 
position set in; or if the solution be made a little too acid or 
a little too alkaline, the original proteins are broken up and 
lost. Egg-white, which is composed chiefly of the protein egg- 
alburnin, exemplifies this. 

Great difficulties are encountered in obtaining most proteins 
in a condition of sufficient purity to ensure that their analysis 
will yield more than a rough quantitative significance. Their 
molecular structure is extremely intricate. But, by boiling with 
dilute acid, proteins may be broken down into simpler sub- 
stances which for the most part belong to the group amino- 
acids, and, as these are closely concerned with food digestion, 
pupils should certainly know something about them. 

It used to be thought that when once the digestive process 
had converted the food into soluble products, the molecules 
of which were small enough to permit of their diffusion through 
the mucous membrane of the alimentary canal into the blood, 
the whole object of digestion had been accomplished. And 
it is, of course, true that peptones are easily soluble and will 
diffuse, slowly, through membranes; they would seem, there- 
fore, to answer the criterion of fully digested proteins. But 

( K 72 ) 16 



220 SCIENCE TEACHING 

we now have reason to believe that the digestion of proteins 
does not stop at the peptone stage but continues until the free 
amino-acids are liberated. 

This breaking down of the proteins of the food into their 
constituent amino-acids during digestion is a process which is 
not, strictly speaking, to be included among metabolic changes, 
for it occurs in the cavity of the alimentary canal (it is assumed 
that the pupils knew, from the earlier stages of their zoology 
course, that the alimentary canal is, morphologically, a mere 
tube external to the actual tissues of the body).* The term 
metabolism is reserved for such chemical changes as take place 
in the living cells themselves. During digestion, the proteins, 
and indeed the foodstuffs in general, are merely prepared for 
the metabolic changes which they have still to undergo. It 
is only when the amino-acids have been absorbed from the 
digestive tract that their metabolism begins. 

A well-prepared Sixth Form boy should be able to under- 
stand this fundamental principle clearly. And he ought to 
be able to cover, in an elementary way, the following ground: 

1. The general nature of digestion and metabolism. 

2. Proteid digestion. Nitrogenous equilibrium. Proteid 
starvation. 

3. Fats and their metabolism. 

4. Digestion of carbohydrates. Diabetes and insulin. 

5. The human machine. Fuel requirements and energy 
output. 

6. Enzymes and ferments and their activities. Enzymes 
considered as catalysts. 

7. Hormones as excitants. How the activities of the different 
parts of the body are probably correlated. 

A short lesson on the accessory food substances, vitamins, 
should be included. No practical work is possible, too little being 
known about vitamins, but certain broad facts should be taught. 

* For beginners, illustrate this by wrapping a closed bag round the hand. The 
hand is not " inside " the bag. Neither is the food in the alimentary canal " inside " 
the body. The alimentary canal is, morphologically, a mere continuation of the 
body-exterior. 



HUMAN PHYSIOLOGY 221 

We huve no conception of the mode in which these bodies 
work. They do not correspond to our ordinary idea of enzymes 
or ferments. They are present in fresh food and tend to be 
destroyed by the processes of cooking and preserving. They 
are necessary for continued health, being essential for the 
carrying out of vital processes; but it is no longer supposed 
that they are chemically related to the amines, as the name 
vit-amins suggests. It is, however, certain that they are definite 
chemical substances, and they should not be referred to as 
if they were merely mysterious " principles ". 

But practically nothing is known of their chemical com- 
position. In foods they exist in incredibly small amounts, and 
yet they are known to be extraordinarily active and to be essential 
for health. Nobody has ever handled an isolated vitamin or 
seen one. They are tested by their effects on animal feeding. 

The results of chemical research, combined with subsequent 
experiments on animal feeding, have shown that there are two 
groups of vitamins. Some are soluble in water and some in 
fats, these two substances being normal constituents of all 
living protoplasm. Of the fat solubles, the best known are 
" A ", " D ", and " E ". The two best known water solubles 
are " B " and " C ". 

Fat-soluble vitamins are left behind in the i per cent of 
oil not turned into soap during the process of boiling with 
strong alkalies. We feel bound to infer that substances able to 
resist such drastic treatment must have a definite chemical 
constitution. 

The following main facts about the respective vitamins 
may be taught: 

Fat-soluble A. Associated with the fat of milk, and with 
most animal fats, e.g. unrefined cod-liver oil. Necessary for 
the normal growth of young animals, also to prevent rickets, 
a disease in which calcification of bones and teeth is deficient. 
In its absence there is a susceptibility to eye-ulceration, to 
colds, to pneumonia, and to tuberculosis. Vitamin A is present 
in butter, milk, cheese, beef and mutton fat, eggs, water-cress, 
maize, carrots, bananas, and tomatoes. 



222 SCIENCE TEACHING 

Water-soluble B. An anti-neuritic vitamin, fourtd in the 
outer layers of rice-grains and in many other tissues, both 
plant and animal; also in yeast. Beri-beri is a disease amongst 
Eastern peoples who eat white rice. In the absence of vitamin 
B there is a marked susceptibility to nerve trouble (neuritis, 
degeneration of the nerve-tracts). Vitamin B is present in 
the husks of cereals; hence it is present in oatmeal and in 
brown bread; also in white bread made with yeast. 

Water-soluble C. The anti -scorbutic vitamin. It is abun- 
dant in the tomato and in the Cochlearia officinalis (scurvy 
grass), and it is present in oranges, lemons, grape-fruit, water- 
cress, lettuce, &c. 

Fat-soluble D. The anti-rachitic vitamin. It often accom- 
panies A, and thus is found in animal fats, butter, milk, fish, 
oils, &c. Exposure to light compensates for a reduced amount 
of this vitamin. Rays of short wave-length seem to act by 
producing a synthesis of the lacking substance. The substance 
called ergosterol is a powerful absorbent of ultra-violet rays, 
and by adding irradiated ergosterol to such foods as mar- 
garine, the nutritive quality is greatly improved. Until recently, 
cod-liver oil was supposed to be the best available source of 
vitamin D.* 

Fat-soluble E is present in wheat-oil. It is essential to 
fertility, but we know little about it yet. 

It seems clear that the vitamin content of even the poorest 
diet may be restored abundantly by the addition of cod-liver 
oil or fresh milk and butter, a yeast extract, and orange juice. 

Actinotherapy 

Reference was made to light-exposure as a possible com- 
pensation factor for reduced vitamin D. In view of the rapid 
development of actinotheraphy, one or two lessons on the 
subject are advisable: e.g. the physical basis of light therapy, 
natural and artificial sources of ultra-violet radiation, the bio- 

* In Nature for March 3, 1928, there is, an interesting letter dealing with birds' 
methods of feeding their young with feathers, with the apparent object of supplying 
anti-rachitic vitamin D. 



HUMAN PHYSIOLOGY 223 

logical action of ultra-violet rays, the use of ultra-violet rays 
in the home, ultra-violet lamps, dangers and precautions. The 
supplement to Nature, 2ist April, 1928, contains several useful 
articles on the theory and practice of the subject. 



CHAPTER XIX 

Embryology 

Why Embryology should be Taught 

One reason, perhaps the main reason, for including in a 
school biology course at least a few lessons on embryology is 
that pupils may be able later to understand the inner meaning 
of much of the evidence adduced on behalf of the hypotheses 
of evolution and heredity. In Darwin's opinion, the facts of 
embryology afforded the most conclusive of all evidence in 
favour of the hypothesis of evolution. The resemblance be- 
tween the embryos of various animals is much closer than the 
resemblance between the adults. The fact that the embryos 
of such vertebrates as birds, and snakes are almost indistin- 
guishable from one another at the earliest stages of their 
development, and the fact of similarity, in embryos, of homo- 
logous parts which later on become differentiated, point back 
to common ancestors. A strong confirmation is afforded by 
the survival of vestigial organs. It follows that the hypothesis 
of evolution can hardly be made intelligible to pupils unless 
they have some knowledge of at least the bare fundamentals 
of embryology. 

The pupil must understand that embryology has for its 
subject-matter the growth of animals from the time they first 
appear as germs in the bodies of their parents until they reach 
the adult condition and are able to produce similar germs 
themselves. It thus includes the study of a complete life- 
cycle. In practice, of course, the study of the adult form 



224 SCIENCE TEACHING 

precedes the study of all other stages of the life-history. It 
is, however, extremely difficult to obtain, with any complete- 
ness, knowledge of the whole course of any given life-history. 
Such knowledge as we have is usually the result of inferences 
from comparisons of many individuals of various ages. In 
the case of the vast majority of animals, only a few scraps of 
life-history are known, and the piecing together of these is a 
formidable task. 

The pupil must also understand that " birth " is nothing 
more than a passing phase in the life of a new organism. True 
there are then certain new phenomena. For instance, when a 
child is born, the nerve centres which regulate the complex 
apparatus of breathing start into instant and effective opera- 
tion. When the mother's breast is presented to the child, the 
child immediately starts sucking, the nerve centres which 
regulate this intricate series of actions beginning to work as 
if they had already served a long apprenticeship. A young 
duck swims with orderly strokes as soon as it leaves the shell. 
We cannot explain how such marvellous evolutionary results 
have been reached. 

The provision of suitable practical work for pupils is a 
serious difficulty, and yet without practical work the subject 
can neither be presented with much reality nor be appreciated 
at its proper value. Much will depend on the material avail- 
able, and concerning that the nearest university professor of 
zoology may always be consulted. 

The Basic Facts to be Taught 

The main facts to be impressed on the learner's mind are: 

1. That an egg-cell after fertilization enters on a series of 
changes collectively called development and that embryology 
is concerned with the study of these changes. 

2. That the egg after it has begun to develop is called 
the embryo , a term (or fcrtus in mammalian embryology) which 
always applies to the unborn young. 



EMBRYOLOGY 225 

3. That the embryo may complete its development either 
within the egg-shell or egg-membrane, or within the parent 
body, though it may become free at some earlier stage as a 
larva. In the former case the young at birth very closely 
resembles its parent; in the latter it is very dissimilar, and the 
larva has to undergo a metamorphosis before it reaches the 
adult state. 

4. That the developing embryo exhibits a progressively 
complex structure, the various steps in the production of which 
occur in an orderly sequence. 

5. That the first stages in the development are more or 
less similar in all animals, and that thereafter the development 
of animals of different groups diverges. 

6. That cell-multiplication and the subsequent growth of 
the daughter cells are the general and fundamental processes 
conditioning differentiation. 

7. That the first stages consist of the repeated division of 
the fertilized egg by mitosis, until a large number of cells are 
produced. 

8. That as the egg-segmentation proceeds, localized growths 
resulting in enlargements and constrictions occur; that cell- 
aggregates gradually form cords, sheets, and masses; that 
delamination occurs, i.e. the splitting of sheets into separate 
layers; that in these sheets folds resulting in evaginations and 
imaginations are produced, i.e. sheets of cells are folded out- 
wards and inwards. 

9. That these folds, due to unequal rapidity of growth, 
are the chief factor in moulding the organs and thus in giving 
the general form to the embryo. 

10. That the differentiation of the cells and the parts of the 
embryo continues until the adult morphology is completed. 

Practical Work 

The blastula and gastrula stages of segmentation should be 
clearly recognized. The method of development of those two 
forms may be easily shown by making rough models from 



226 SCIENCE TEACHING 

strips and small sheets of clay or plasticine with the* surface 
roughly marked to indicate cells. Only a little skill with the 
fingers is required to illustrate in this way the earlier stages 
of embryonic development. Blackboard sketches are not 
enough; some learners simply cannot visualize three-dimen- 
sional bodies from such sketches. 

It is probably best to begin practical work by examining 
hens' eggs taken from an incubator, and studying the contained 
chick embryos. The embryo may be studied whole, and most 
of the main structures easily identified during the first two or 
three days of incubation. Eggs may be opened every 6 or 8 
hours during the first 4 or 5 days of incubation. The best 
stages for early examination are those at the end of the 24th, 
33rd, 48th, and yand hours. The gradual formation of the 
several organs may be easily observed. The eggs should be 
opened in normal saline solution at 40 C. It is a simple matter 
to cut round, with scissors, the germinal disc, to float the 
embryo off the yolk, to remove the vitelline membrane, and 
then to float the embryo, dorsal side up, on to a glass slide. 
It should be remembered that the egg is normally laid in the 
gastrula stage. After the laying, the egg cools, and develop- 
ment ceases until incubation is begun. 

Frogs 1 eggs are also suitable material for study. The eggs 
are relatively large because they contain a considerable quantity 
ot yolk. The jelly secreted by the oviducts of the frog at the 
time of laying causes the eggs to adhere in masses, and this 
jelly must be removed before an attempt is made to study the 
egg or embryo. The eggs may be studied in cleavage under 
the low power or with a hand lens; sections of the blastula 
may be made and sketched; also sections of the gastrula; 
also, at successive later stages, sections of the embryo. The 
time between laying and hatching is i to 3 weeks, according to 
the species and to the temperature of the water. 

The eggs of the star-fish also afford excellent material for 
the general study of typical early embryonic development. 

The process of embryonic development as a whole cannot 
clearly be shown in the case of any single animal. Different 



EMBRYOLOGY 227 

.animals must be selected according to the particular purpose 
in hand. The tadpole (the larva of the frog), for instance, may 
be utilized for a simple study of the later stages. Tadpoles 
may be taken as soon as hatched, suitably fed, their further 
development watched and described, and the times when 
changes take place noted, especially the appearance of the 
hind limbs, then of the fore limbs, then of the rapid meta- 
morphosis into a frog. 

It is important for the pupil to be able to visualize the 
changes in the developing embryo. He should first examine 
the whole embryo at as many different stages of its develop- 
ment as possible; then perhaps dissections; then the whole 
embryo in serial sections. The complete picture of the develop- 
ment from egg to adult may thus be gradually visualized. 
The older embryologists had to be satisfied with the knowledge 
gained from the study of the entire embryo and of minute 
dissections. Now the egg or embryo is cut into a number of 
exceedingly thin slices, arranged in order on glass slides, and 
examined under the microscope. With a little practice, the 
necessary visualization may be satisfactorily effected. 

Mitosis 

The teacher who attempts practical work in mitosis must 
be a skilled microscopist. If he is not, he should use prepared 
slides instead. After all, many of the phenomena of mitosis 
are at least as much a matter of inference as of observation. 

The germ-cells of ascaris are perhaps the best material for 
studying the different stages of mitosis. The eggs are of fair 
size, division is fairly rapid, and the chromosomes are large 
and few in number. Under a low power, the cavity of the 
oviduct may be seen to be filled with eggs. Longitudinal 
sections of the oviduct may be made in the region where the 
eggs are developing, and it is possible that some of the various 
stages of mitosis may be found when the eggs are then examined 
under a high power. It may not be easy to find any particular 
stage, especially as some of the eggs will probably not be cut 



228 SCIENCE TEACHING 

in the right plane to show the mitotic process to advantage. 
Successful work demands a skilful hand. 

The reproductive organs of several of the lower animals at 
the time of sexual activity also provide suitable material, as 
the cells are dividing rapidly to produce the new cells. The 
testis of the crayfish is often used. The root-tips of plants 
grow very rapidly in some cases and are therefore favourable 
places for finding the stages of mitosis. Make longitudinal 
sections through the tip. The growing region where the divid- 
ing cells are situated are a little back from the root-cap. 

Whether or not any practical work is done, the phenomenon 
of mitosis must be clearly understood, less perhaps for a clear 
general understanding of embryology as such than for a clear 
realization of the nature of chromosomes and the part they 
play in heredity. See the next chapter. 

Animals and Plants 

The pupil should note the essential distinction between 
the embryology of animals and the embryology of plants. In 
the higher animals the embryology is carried out once for all; 
for instance, the limbs are laid down and, normally, no further 
members are formed. But in plants the formation of new 
members is continued throughout the whole of active existence. 

The "Recapitulation" Theory 

The pupil must also understand what is meant by " re- 
capitulation " in development: any particular plant or animal 
seems to begin to develop in much the same way as the embryos 
of all the plants or animals below it in the evolutionary scheme 
of classification. The fundamental law of biogenesis is that the 
individual in its development recapitulates the development of 
the race. If such a law were substantiated, it would bind up all 
the innumerable phenomena of development into one coherent 
scheme. But it has now been demonstrated that this law of 
parallelism is strictly limited, though biologists agree that any 



EMBRYOLOGY 229 

given liic-mstory contains ancestral elements. The developing 
chick is, at a very early stage, demonstrably a vertebrate, and 
does not recapitulate the organization of a polyp or a worm or 
a mollusc. The recapitulation is never that of the whole organi- 
zation of a lower animal, but only that of particular parts. 
Any given life-history exhibits many features which in no way 
reflect the characters of ancestors. And yet if evolution be 
a fact, it would not be unreasonable to expect that the recapitu- 
lation would be complete, and it is admittedly true that the 
early stages of embryonic development seem to be extra- 
ordinarily alike in all animals. If in the later stages there is a 
recapitulation, many of the steps must be rapidly hurried over 
and practically omitted. 

Common to all embryos is the origin in a single fertilized 
cell, the division and subdivision of this cell, the formation 
of a mass of cells, and then the folding up of this mass. But 
with this folding, the mass begins to mould itself in a specific 
way. What is the origin of this differentiation? Presumably 
it is traceable to the parents, for ultimately the embryo becomes 
a copy of the parents, not a perfect copy it is true, but a recog- 
nizable copy and yet a copy with differences. This fact is 
the natural introduction to the study of heredity. 

Human Embryology 

It is not necessary to touch upon human embryology, 
except perhaps in a very incidental kind of way. In taking 
up heredity and evolution subsequently, the teacher may 
safely presume inferential knowledge. Sixth Form boys and 
girls in their second year are generally quite sensible over 
matters of this kind. 

Material and Books 

There are many series of prepared embryological slides that 
may be purchased. An excellent series of the embryo chick, 
seven in number, may be obtained from Messrs. Watson of 



230 SCIENCE TEACHING 



i 



Holborn. Messrs. Flatters and Garnett also have a very useful 
series of preparations, the later stages being mounted in glass 
jars. In Lull's Organic Evolution there are figures of a com- 
parative series of embryos, at four different stages, of a fish, 
salamander, tortoise, chick, pig, calf, rabbit, man. See also 
Lull's Evolution of Man (fig. 23). For methods of collecting 
embryos, killing, fixing, preserving material for microscopic 
work, mounting entire embryos, embedding and section cutting, 
see Shumway's Vertebrate Embryology. Several of the Ameri- 
can books give particularly useful hints on practical work, 
but it is doubtful if, even now, there are better instructions for 
practical work than those given in a book written nearly fifty 
years ago by Professor Michael Foster and Professor Francis 
Balfour. See pp. 423-60 of the 1893 edition. The details for 
obtaining and studying chick embryos and for cutting sections 
are clear enough for any novice to follow. Another suggestive 
little book is Mr. de Beer's Experimental Embryology. 



CHAPTER XX 

Heredity 

j 

The Basic Facts for the Pupil 

Practical work on the subject-matter of this chapter and 
the next is almost out of the question, and all facts must be 
supplied second hand. From the point of view of science 
training there is much to be said for making the respective 
courses of instruction as short as possible. As, however, so 
comparatively few laymen seem to have clear notions of the 
actual evidence on which the theories of heredity and evolution 
are built, the least that should be done in a Sixth Form is to 
present the evidence, clearly and logically, in some half-dozen 
lessons on each subject, and to show to what extent the generally 
accepted inferences from the facts are justified. 



HEREDITY 231 

So fa as heredity is concerned, lead the pupils to under- 
stand, first, what the term implies that living organisms can 
produce their like, the resemblance, though never absolutely 
perfect, extending to the most minute details of structure and 
function; secondly, that any theory of heredity, to be accept- 
able, must account for all the main facts of the general likeness 
of parent and offspring. In particular: 

1. Variations occur in the offspring, i.e. characters that are 
not exhibited in the same degree by the parent. 

2. Specific similarities occur in the offspring, i.e. characters 
that occur in one or both parents. 

3. Characters may occur in the offspring that do not occur 
in either parent but that did occur in a grandparent or in some 
remoter progenitor. 

4. Characters acquired by a parent in the course of his or 
her life, as the result of apparent interaction with the environ- 
ment, seem in some cases to reappear in any offspring subse- 
quently born. (This has given rise to great controversy.) 

Further basic facts for the pupil to understand are: (i) 
the difference between (a) continuous, and (b) discontinuous or 
saltatory variations; and (2) the difference between (a) innate 
or germinal variations (whether continuous or discontinuous) 
and (b) acquired characters. The innate or germinal variations 
is that important remainder left after there have been sub- 
tracted from the whole not only all the differences of age and 
sex but also all the acquired characters; they are those which 
are inherent in the individual, and are largely independent of 
the manner of life. These various terms are the current coin 
of all discussions on heredity and must be fully grasped. 

Hypotheses of Heredity 

Most of the theories that have been put forward to account 
for all the facts are ultimately based on a relatively small 
number of actually observed processes of cell-division the 
processes of maturation, mitosis, and segmentation and the 



232 SCIENCE TEACHING 

inferential evidence derived from these processes. Ftr at least 
two centuries, the sperm-fertilized ovum has been looked upon 
as containing in some way the physical basis of the new organism. 

Some of the hypotheses have a statistical basis; others are 
unrelated to statistical experiments of any kind. Nearly all 
scientific hypotheses are, of course, based on a certain number 
of observed facts, and to that extent are statistical. Even 
Avogadro's hypothesis originated in the few experimental facts 
constituting the law of Gay-Lussac. Any hypothesis whatever 
should be based on facts of observation and experiment, and 
the descriptive scheme put forward should enable us (i) to 
trace out in detail the processes which lead to the facts observed; 
and (2) to use it as an instrument for predicting occurrences 
not yet observed. The pupils should be encouraged to try to 
apply these tests to the various hypotheses of heredity, and to 
ask themselves if they feel more satisfied with one particular 
hypothesis than with the others, and, if so, why. 

The principal hypotheses may be thus tabulated, and the 
pupil be instructed to memorize them: 

1. Non-statistical hypotheses: 

(1) The Preformationist hypothesis. 

(2) The Epigenesis hypothesis of Wolff and others. 

(3) Lamarck's hypothesis of transmission of acquired char- 
acters. 

(4) Darwin's Pangenesis hypothesis. 

(5) Weismann's Germinal Continuity hypothesis. 

2. Statistical hypotheses: 

(1) Galton's and Karl Pearson's hypotheses. 

(2) Mendel's hypothesis. 

We append a brief summary of such facts as should be taught. 
The Preformationist Hypothesis. This was the favourite 
hypothesis during the seventeenth, eighteenth, and earlier part 
of the nineteenth centuries. The germ of one of the two 
parents was supposed to contain within itself a complete 
miniature model of the parent; it had only to be unfolded or 
evolved or increased in size in order to become the new animal. 
It was taught that within this miniature was a second, within 



HEREDITY 233 

the second a third, and so on for all future generations. Sup- 
porters of this juggler's nest of boxes asserted that nothing new 
was ever generated, that everything pre-existed. The absurd 
hypothesis held sway until Wolff's demonstration of the 
gradual development, in the case of the chick, of the apparently 
simple into the manifestly complex. Wolff showed conclusively 
that the development was epigenetic, taking the form of a true 
series of transformations. 

The Epigenesis Hypothesis. This hypothesis assumes that 
the evolution of an animal consists of a gradual increase of 
complexity from what at first appears to be comparatively 
simple, and that in this way something essentially new really 
does arise. But just as the preformationists could not account 
for the origin of their miniatures, so Wolff was unable to explain 
satisfactorily the demonstrated fact that the end-result of epi- 
genetic development was an individual similar to its parents. 

Lamarck *s Hypothesis. Essentially, Lamarck's hypothesis 
was that " acquired " modifications are being continually pro- 
duced and perfected by every organism during its life, and that 
they are at least partially transmitted to its offspring, so that 
each generation will be rather better adapted to its surroundings 
than its predecessor. In this way, the great length of the neck 
of the giraffe would be explained by the continual striving 
through many generations to reach higher limbs in the trees; 
and the limbless condition of snakes would be explained by 
the gradual loss of limbs through disuse. 

Darwin's Pangenesis Hypothesis. In the pangenesis hypo- 
thesis, the germinal cells are supposed to contain samples 
contributed by all parts of the body, and in the embryo the 
samples give rise to parts similar to those from which the 
samples came. Darwin's hypothesis was an hypothesis of this 
kind. Darwin assumed that every cell of the body, not too 
highly differentiated, throws off at each stage of its development 
characteristic gemmules, or small particles, which later multiply 
by division and give rise to cells like those from which they 
originated. These gemmules, which are conveyed in the blood, 
become specially concentrated in the germ-cells of both sexes, 



234 SCIENCE TEACHING 

or in buds. In the development of the embryo, these gemmules- 
unite with others like themselves and, being aggregated in the 
germ-cells, they invest the germ-cells with the power of develop- 
ing into a complete organism; but during the development of 
the embryo, some of the gemmules may remain latent through 
several generations before they become active. This ingenious 
hypothesis certainly accounts for the known facts of heredity, 
and it affords a simple explanation of the transmission of 
characters which may remain latent for several generations. 
But though the gemmules may be conceived, they cannot be 
perceived. There is just a slight possibility of the hypothesis 
being in harmony with facts not yet known, but we cannot 
say more than this. Gemmules may have an objective existence. 
We do not know. 

Weismann' s Germinal Continuity Hypothesis. This is an 
hypothesis of both heredity and racial evolution. It is based 
on the notion that the continuity of characters in heredity is 
to be thought of as the result of a continuity of material between 
parent and offspring, that continuity holding good through an 
indefinite number of generations. The essence of the hypo- 
thesis is germinal continuity. Weismann taught that the germ- 
cells are to be regarded merely as parts of an unbroken line of 
germ-plasm, the bearer of the heritable qualities; that in 
certain circumstances this germ-plasm frothed up and pro- 
duced a great excrescence, the somatoplasm, the body of the 
next generation, and in that somatoplasm the germ-plasm 
continued its existence; that the germ-plasm thus passed on 
from generation to generation, but that the great excrescence 
thrown off from time to time, the animal " body " as we com- 
monly call it, in due course died. Weismann postulated that 
an individual is like his parents not because he is produced 
by them but because both parent and offspring are produced 
from the same stock of germ-plasm. 

In the division of the primitive germ-cells, the nuclear 
substance, the chromatin (so-called because it absorbs stain) 
becomes arranged in the form of a definite number of rods or 
chromosomes. Points for explanation: the general phenomenon 



HEREDITY 235 

of mitosis: the cell and its cytoplasm, the nucleus and its con- 
tained chromatin, the centrosomes, the formation of the chro- 
mosomes or idants (a definite number in each species, said to 
be 48 in man), the halving of the chromosomes before con- 
jugation (i.e. the process of maturation), and the assumed 
parental contributions of the chromosomes. The pupil is now 
in a position to understand the nature and inner significance 
of the germ-plasm hypothesis: it is assumed that each chromo- 
some contains germ-plasm derived from the ancestors of both 
parents; that therefore the chromosomes contain an accumu- 
lation of material derived from earlier ancestors on both sides; 
that each chromosome is definitely organized into a number 
of ids, each id seeming to contain within itself, in some way, 
all the generic, specific, and individual characters of a new 
organism, in short, a complete inheritance; that the ids are 
similar but not exactly the same, and that the animal wiiich 
develops is a compromise between the various ids; that each 
id is itself an organization with individual constituents called 
determinants; that each determinant is concerned with the 
formation of some special organ in the embryo; that each 
determinant is itself usually composed of a group of biophors y 
the minutest vital units but each an integrate of numerous 
chemical molecules. Thus the id represents the complete 
individual, the determinants its different parts and groups of 
cells, the biophors the " characters ". It is argued that the 
biophors must actually exist, since every phenomenon of life 
must be connected with a material unit of some kind. 

Weismann's hypothesis is extraordinarily ingenious, and 
adequately covers all the facts. But it is based upon inferences 
drawn from the all too scanty observations of chromosome 
division into ids, and it is very doubtful if the assumption of 
the continued subdivision into determinants and biophors is 
justified. 

Had Darwin lived, he would probably have abandoned his 
gemmules and have concentrated on the phenomena of nuclear 
division. The great majority of present-day investigators are 
definitely of opinion that the nucleus is the seat of the hereditary 

(K72) 17 



HEREDITY 237 

Francis Galton, who was followed up by Karl Pearson, 
dealt with such factors as stature, colour of the eyes, disease, 
the artistic faculty. The characters in sweet peas and in moths 
were also investigated. Galton's ascertainment of the facts 
of correlation between the characters of the child and that of 
its more remote ancestors affords some confirmation of Weis- 
mann's hypothesis of the continuity of the germ-plasm, so far 
as this hypothesis can be said to include an accurate description 
of known facts. Galton's law of ancestral inheritance has a 
foundation which is firm thus far that it is based upon 
observations which have subsequently been systematized: the 
two parents between them constitute on the average one-half 
of the child's inherited faculty; each contributes J. The 
4 grandparents amongst them also contribute , or each r V- 
The sum of | + | + i + iV + ... is equal to i , as the law 
would lead us to expect. This law is purely statistical, dealing 
only with large averages. It is merely a summarized record of 
actual observations. Its hypothetical element is small. 

Mendel undertook a very different class of investigations 
relating to the laws of inheritance in hybrid varieties. He 
hit upon the device of selecting one at a time out of the many 
thousands of characteristics of an individual, and finding out 
how that one is transmitted through several generations. He 
experimented in 1866, chiefly on varieties of peas. The records 
of his work were brought to light in 1900, and Mr. Bateson 
drew attention to them. 

Mendel had taken for his problem the question as to the 
exact manner in which the definite and true-breeding varieties 
within a species are related the one to the other. He con- 
centrated his attention not upon the individual as a unit but 
upon the mode of inheritance of pairs of sharply contrasted 
characters. The method he adopted was that of hybridization, 
and he kept accurate pedigree records, showing the ancestry 
and the characterization of each individual. He counted the 
number of individuals in each generation, and the numbers 
of dissimilar kinds, and was thus able to give an exact mathe- 
matical statement of his results. In this way he reduced the 



238 SCIENCE TEACHING 

phenomena of inheritance to a measurable basis. Out of his 
experimentation emerged clearly the verifiable fact that when 
one or more pairs of alternative characters are involved in a 
breeding experiment, there is in the second hybrid generation 
an orderly reappearance of these characters in definite numerical 
proportions. 

When the records of MendePs work were brought to light 
in 1900, it was recognized that in them was confirmation and 
extension of the essentials of Weismann's hypothesis, but the 
work of recent years has led to a modification of Mendel's 
laws. The revised Mendelian hypothesis is like the Weismann 
hypothesis in this fundamental respect: it implies that the 
germ-plasm of organisms is not an invariable whole but an 
organization of units or factors which can be dissociated and 
recombined in various ways. Mendel's units are called genes. 
Breeding experiments seem to be generally confirmatory of 
Mendelian principles. 

Further points for class-room explanation: dominants and 
recessives; the law of inheritance; hypothesis of gametic 
segregation. Mendel's experiments with peas might be repeated 
in the school garden, the annual results being recorded for 
consideration by boys in successive Sixth Forms. 

Main Principles now Generally Recognized 

There is a consensus of opinion that the secret of heredity 
is to be found in the fertilized germ-cell. The pupils must 
therefore know: 

1. That although the individuals of a generation die, life 
is transmitted to the next generation through the function of 
reproduction. 

2. That, in the higher forms of life, this consists in the 
union of the gametes, egg and sperm, to form the zygote, the 
new individual of the next generation, embodying all the 
possibilities of individual development and of racial per- 
petuation. 

3. That although each of the two parents contribute but 



HEREDITY 239 

a single cell so minute as to be far beyond the limits of the 
unaided eye, yet these gametes are the only material link 
between the generations, and across this extraordinarily narrow 
bridge everything organic which any generation can receive 
from its predecessor must pass. 

4. That the zygote exhibits none of those details of struc- 
ture and function which, when the individual has assumed 
its definitive form, will enable the observer to describe and to 
classify it, yet in this fertilized egg there must surely be 
something that predetermines much of the individual's future 
morphological, physiological, and psychological limitations. 

The pupil must also know that although the phenomenon 
of metosis is perplexing and still full of doubt, and although 
we have very little exact knowledge of the chemical nature of 
chromatin, yet it has been definitely established: 

1. That chromatin is intimately related to the activities of 
the cell as a whole. 

2. That it has a definite architecture and disposition within 
the nucleus. 

3. That during cell-division it assumes a condensed appear- 
ance, and displays its organization as a number of units, the 
chromosomes. 

4. That the number, size, form, and behaviour of the 
chromosomes are constant in a species, and characteristic of 
that species. 

5. That even when the chromatin is thus condensed in the 
form of chromosomes, it still retains its organic contact with 
the non-chromatic part of the cell, of which it is but a part 
though an essential part. 

6. That no development is possible at all in the absence 
of at least one haploid set of chromosomes. 

7. That as the result of countless experiments, the chromo- 
somes are regarded as the only identifiable cell-organs which 
can satisfy the demands made upon the germ-plasm, and that 
in their observed behaviour are realized the precise condition 
of hereditary transmission. 



240 SCIENCE TEACHING 

8. That although Weismann's ids, determinants, and bio 
phors are purely hypothetical, Weismann was undoubtedly 
right in locating his units in the chromosomes; and that it is 
now fairly definitely established that each chromosome bears 
a certain number presumably a vast number of the heredi- 
tary factors or genes (as the Mendelian units are called), that 
each gene has its own particular place within a particular 
chromosome, and that there is an exact parallelism between 
the chromosome-containing genes and the distribution of the 
hereditary characters. 

9. That the chromosomes in the immature gamete are 
present in pairs, and that one member of each pair has been 
received from each parental organism. 

10. That in the ripe gamete, only one member of each pair 
of homologous chromosomes is present, and that the sorting 
of the chromosomes during the maturation of the gamete is 
at random. Hence, 

(i) since there are equal chromosome contributions from 

each parent, 

(ii) since there is a random assortment at maturation, 
(iii) since there is a chance recombination in fertilization, 
(iv) since there is a possibility of an inner reorganization 

of each chromosome through its most intimate 

association with another of identical structure but 

different content, 

it must follow that an almost infinite range of new com- 
binations of character is provided, and thus the chromosome 
mechanism can supply the variations upon which the forces 
of selection can operate. 

It is advisable in teaching to emphasize the fact that much 
of what is described in the process of mitosis is quite invisible 
even under the highest powers of the microscope, owing to 
the fact that almost all the parts of the living cell are really 
quite transparent; and that it is a little dangerous to assume 
that the phenomena seen in a stained (and, therefore, presum- 
ably dead) cell represent a true picture of the living cell: it 



HEREDITY 241 

is just jjussiule that the appearances are merely incidental to 
the death of the cell. 

Thoughtful pupils are generally sceptical about the possible 
existence, in such a microscopic thing as the zygote, of the 
necessary millions upon millions of units representing all the 
different parts of the future body. They recognize the necessity 
of assuming within the zygote a very complex machinery of 
some kind, but they want something that can be visualized, 
and not merely conceived. They are less sceptical about the 
Mendelian gene than about Weismann's biophors, but they 
tend to pause when they think of the still necessary vast 
number of genes to correspond to all the unit characters that 
can be observed in experimental breeding. There is, of course, 
a certain amount of evidence that genes actually exist and are 
arranged in pairs, and that the pairs are grouped. The safer 
plan is, however, to tell the pupils that the genes are purely 
hypothetical, but that the results of experimental breeding are 
such as to be readily explained if it be assumed that genes do 
exist, and are grouped in a particular way. Even the remark- 
able results of the breeding experiments with Drosophila melano- 
gaster throw no certain inner light on the machinery concealed 
within the chromosome, and yet Morgan and his American 
coadjutors can now produce, so it is said, almost any kind of 
fly to order! 

Occasionally a boy will notice that the phenomena of 
mitosis, especially as displayed in some of the conventional 
diagrams, present a symmetry which is strikingly analogous 
to that of the phenomena of a bipolar electric field; and, if 
he happens to have a liking for chemistry, he may be inclined 
to look upon a dividing cell as an electrolytic phenomenon, 
full of wandering ions. Even if mitosis can be explained as 
the result of a conflict between surface tension and its opposing 
forces (as some biologists suggest), this is carrying the explana- 
tion only one stage farther back. Possibly we may account 
for the phenomena if we assume that the same forces are at 
work as in phenomena of grosser nature, but the assumption 
is not justified. To leave upon the pupil's mind the impression 



242 SCIENCE TEACHING 

that the living cell is exclusively a thing of physics and chemistry 
is not justifiable. It is more than that, it is dishonest, because 
we do not know. Even if all the factors of heredity are ultimately 
traced to chromosome units of some kind, we shall only be 
able to explain the mere mechanism of heredity. The essential 
phenomena of life will still remain unexplained. 

Not the least important thing in the subject of heredity 
for a boy to understand is that the great controversial question 
in all hypotheses of heredity is the inheritance of acquired 
characters. An acquired character is a structural change in 
the body, of a kind which involves some change from the 
normal structure of the species to which the individual belongs. 
It is acquired and remains permanent during the life-time of 
the individual, and can be shown to be traceable to a change 
of environment such as climate, or to functional use or disuse 
such as is involved in specialized habits. From the point of 
view of any hypothesis of germ-plasm, the question whether 
a somatic modification of this kind is heritable or not is equi- 
valent to the question whether such modification is accompanied 
by a specific change in the germ-cells, such that the offspring 
will inherit the modification which the parent acquired. When 
the evidence as to the inheritance of acquired characters has 
been presented pro and con, the verdict is not proven, and this 
impression should be left on the pupil's mind. 



EVOLUTION 243 

CHAPTER XXI 

Evolution 

The Great Range of the Subject 

In the narrower sense, evolution and heredity are very 
closely allied subjects, but the term evolution was used by 
Lyell to denote the moulding of the earth by natural forces. 
Darwin did not employ the term at all in his book The Origin 
of Species. In its broader sense, we may think of evolution 
as the ascent of man from the lower animals, the ascent of the 
lower animals from some primordial form of life; and perhaps 
we may cross the bridge to non-living matter, and consider 
the origin of the earth and even of the solar system. It is 
well at the outset to impress upon the pupil that, in consider- 
ing the process of evolution, we are still held up by two un- 
solved problems: (i) the origin of life, (2) the origin of species. 
Some account of the rival theories of the origin of life should 
be included in any biological course. In the study of evolution 
in the ordinary sense, the central features are the origin of 
species and the Darwinian theory that the almost inexhaustible 
variety of living plants and animals have arisen by descent 
from a few stocks, or perhaps from only one stock, of simple 
ancestors. 

So far as difficulty of understanding is concerned, the 
subject is well within the range of Sixth Form work. Of neces- 
sity it has to be presented more or less in lecture form. Prac- 
tical work is hardly possible unless, perhaps, the teacher is a 
keen Mendelian. The greatest teaching difficulty is to get at 
basic facts facts which are acceptable generally, and from 
which sound deductions may be drawn. The literature bearing 
on the subject has become so extensive, and in many of even 
the best books facts and theories are so inextricably inter- 
mingled, that the unravelling is a formidable task. From the 



244 SCIENCE TEACHING 

teaching point of view, the following is probably the most 
satisfactory sequence of topics. It is reasonably logical, and 
an intelligent pupil ought not only to be able to thread together 
the facts and the arguments deduced therefrom but to be 
convinced of the probability of the truth of the main thesis , 
even though we are still really ignorant of the actual nature 
of the evolutionary process at work. 

A Suggested Sequence of Topics 

1. ORGANIC EVOLUTION ACCEPTED AS A FACT. Organic 
evolution is now regarded by most educated people as a definitely 
established fact. The old idea of the special creation of different 
species has been abandoned. Bacon, Descartes, Leibniz, and 
Spinoza all held the general idea of evolution. Buffon was 
the first naturalist who expressed clearly the idea that the 
unity of plan in the structure of animals may be due to com- 
munity of origin. Linnaeus hesitated. Cuvier opposed. 
Lamarck opposed at first but changed his mind and became 
a thorough-going evolutionist. Darwin brought forward 
evidence which convinced the majority of intelligent 
people. 

2. SPECIES AND THEIR ORIGIN. Nobody asserts that cats 
are the ancestors of dogs or dogs of cats: the differences between 
them are too great. Dogs have 42 teeth, cats only 30, and there 
are all sorts of other differences, just as fundamental. But it 
is generally believed that dogs and cats probably had a common, 
though very remote, ancestor. And it is universally believed 
that all varieties of the domestic dog had a common ancestor; 
despite differences of appearance, the similarities of structure 
are very close. But when we consider dogs, wolves, and jackals, 
despite the fact that they closely resemble one another in some 
ways (they all have 42 teeth, for instance), the differences are 
too marked for all to be included in one class. They form 
different species] the differences between them are specific. But 
we do group them together under the one genus, " canis ". 



EVOLUTION 245 

One variety of dog is bred from another, one variety of 
pigeon from another; the small differences of a selected kind 
between one generation and the next are accumulated. But 
no one has ever succeeded in breeding a new species from an 
existing species; the difference is too great. It is believed that 
it could be done in time, but it would probably mean tens of 
thousands of generations. And we are not quite sure that it 
could be done at all. 

3. THE EVIDENCE FOR EVOLUTION. Since evolution is a 
process which requires for even its partial accomplishment 
many millions of years, direct evidence is unobtainable. The 
evidence is indirect. The available facts may be classified 
thus: 

(i) Facts from Comparative Anatomy. Morphological com- 
parisons are made of existing allied species. The 
known facts have now become so numerous that their 
cumulative effect is almost overwhelmingly convincing. 

(ii) Facts from Embryology. We have already referred to 
the recapitulation doctrine. How far can it be said 
that the embryo climbs up its own genealogical tree? 
The inheritance of a living creature is possibly some 
sort of condensation of ancestral initiatives which 
compel the developing embryo to retrace, to some 
extent at least, the path taken by the embryos of its 
ancestors. 

(iii) Facts from Paleontology. A comparison of fossil species 
is made with each other, and with living specimens. 
The earlier records are obliterated, but we have 
excellent records of the vertebrates, and it is clear 
that mammals originated from reptiles of the later 
Palaeozoic era. In proportion to the completeness 
of the pakeontological records, the character of the 
testimony to the truth of the theory of evolution seems 
to be more and more unequivocal. We return to this 
subject in the next chapter. 



246 SCIENCE TEACHING 

(iv) Geographical Distribution. Darwin gathered three 
classes of facts during his five years' voyage in the 
Beagle: (i) the manner in which closely allied species 
replace species, in going southward; (2) the close 
affinity of the species inhabiting the islands near 
South America to those proper to the continent; 
(3) the relations of certain living species to extinct 
species. A few examples of these should be 
given. As evidence, their cumulative effect is im- 
pressive. 

(v) Vestigial Organs. The more common should be men- 
tioned. 



4. PRINCIPLES ESTABLISHED FROM THE EVIDENCE. Certain 
principles seem to hold good for all the main groups of 
animals in which checking is possible, and not only for the 
vertebrates: 

(i) When a higher type evolves from a lower, this does not, 
as a rule, lead to the total disappearance of the lower. 
But although representatives of the lower usually sur- 
vive, the total number of species is reduced. 

(ii) As each new type comes into being, we find in general: 
(a) there is a considerable period during which the 
new type is not fully perfected; (b) comparatively 
suddenly, the new type ousts the old from its position 
of dominance. Examples: the early mammals which 
existed during the age of reptiles rose suddenly at 
the close of the secondary period; in mesozoic times 
the mammalian creatures were minute and furtive; 
their successors in the Tertiary era became large and 
dominant. Again, primitive man existed at a low 
stage of development for a long period, and then 
rose quickly to biological dominance, within the last 
ten or twenty thousand years. 

(iii) Once the new type is well established, it usually evolves 
into a number of specialized branches. 



EVOLUTION 247 

5. DARWIN 's VIEWS. (i) Darwin assumed that the minute 
differences which distinguish members of the same brood or 
litter from one another are inheritable, that each variation will 
in turn give rise to other variations in the same direction, and 
that in this way the originally small variations are increased 
by accumulation, (ii) His hypothesis of " natural selection ", 
the universal " struggle for existence ", and " the survival of 
the fittest ". (Explain what he really meant by these things: 
those variations which give some advantage to the individual 
over his fellows are the determining factor.) (iii) His subsidiary 
hypothesis of sexual selection, (iv) He assigned some weight 
to the environment, and to the effects of use and disuse, and 
thus far was in agreement with Lamarck that change in 
environment induces a tendency in animals to vary slightly 
in all directions, and that those variations which happen to suit 
the environment are preserved and affect the character of 
subsequent generations, (v) He regarded the facts of heredity 
as the fundamental facts, and believed that natural selection 
is sufficient to account for the evolution of the most compli- 
cated organs, even though he always admitted the existence 
of other contributory factors. 

The vast influence of Darwin's work is due to the fact 
that he seemed to establish on a firm basis the principle of the 
transmutation of species, as an induction resting on a vast 
accumulation of data obtained by observation and experiments 
of various kinds. From this time onwards, organic evolution 
was no longer looked upon as just a speculative hypothesis, 
but as a well-established principle generalized from indisput- 
able facts. But as to Darwin's mode of " natural selection " 9 
biologists are divided in opinion. 

6. THE THREE MAIN EVOLUTIONARY FACTORS. Biologists 
agree that the three principal evolutionary factors are: (i) the 
living organism itself as a self-adapting creative agent, adjusting 
itself to its environment; (ii) the functions of the living organism, 
their use and disuse; (iii) the environment which stirs the 
organism to action, moulds it, and modifies it. But biologists 



248 SCIENCE TEACHING 

differ as to the relative importance of these; some stress the 
first, some the second, and some the third. 

7. VARIATIONS. Darwin's theory depends essentially on the 
cumulative increase of continuous variations in the direction of 
utility, but some biologists are not convinced that minute 
variations have any selective value, if only because of the enor- 
mous amount of time that would be required to produce such 
changes as the evolution of species contemplates, and they have 
urged the recognition of a theory of saltatory variations, i.e. 
of " leaps " from species to species. All biologists agree that 
variations of one kind or of the other are the real building 
stones of evolution, no matter what may be the cause of the 
variations. 

8. EVIDENCE OF SALTATORY VARIATIONS. The work of 
De Vries, and his law of " mutations "; his term " species " 
appears to correspond to the ordinary term " variety ". The 
work of Mendel; hybridization. What we may learn from 
breeders' work. Bateson's championship of saltatory evolution. 
The geater merit of Mendel's work is that it is experimental, 
hut it is very far from yielding certainty. 

9. MUTATIONS AND DIMINISHED VITAL ENERGY. Mutations 
or " sports " are comparatively common among cultivated plants 
and domestic animals which live under unnatural conditions. 
They are exceedingly rare in wild nature. They seem to render 
their possessors more or less crippled or deformed, as com- 
pared with the type. A pronounced " leap " from type seems 
to result in a diminution of vital energy and therefore of resis- 
tance. Consequently, we must not place too much confidence 
in the assumption that mutations have ever led to forms which 
are capable of survival under the conditions of wild life. 

10. WEISM ANN'S VIEWS. Weismann's views are really an 
extension, to the germ-plasm, of Darwin's hypothesis of 
natural selection. Weismann maintained that there was a 



EVOLUTION 249 

struggle amongst the determinants, and that the most vigorous 
survive. 

11. CAUSE OF THE VARIATIONS. The variations seem to 
originate in changes that first take place in the germ-plasm, 
but how we do not know. No hypothesis that has hitherto 
been put forward gives a satisfactory explanation. Precisely 
how 7 a change in a determinant (or gene, if it be a gene) is 
effected by any of the influencing factors use, disuse, environ- 
ment, and so forth we simply do not know. 

12. THE PRESENT POSITION. The constancy of specific 
characters within the span of observation afforded by a human 
life is the most familiar of all the facts of natural history. Even 
a period of 10,000 years seems utterly insufficient to bring about 
a specific change. Presumably species are still in process of 
formation, the main factors at work being geographical isolation 
with enforced physical and chemical changes, enforced change 
of habit, enforced competition with new environment, and new 
stimuli to germinal energies themselves. But how these various 
factors actually bring about adaptive results in the germ-plasm 
we do not know. The secret is probably hidden in the chromo- 
somes. 

The weight of evidence is probably on the side of dis- 
continuous variations as a prime factor, but the evidence is 
anything but conclusive. 

That the chromosomes consist of units of some kind is 
highly probable, that small variations take place amongst these 
units is also highly probable, and that natural selection then 
sets to work amongst them is scarcely less probable. But we 
cannot say more than this. 

13. ABIOGENESIS AND BIOGENESIS. The work of Tyndall 
and Pasteur, and the general acceptance of the law of biogenesis. 
At present the law is of a negative character; it asserts that, 
at present, there is no known evidence of living organisms 
arising from non-living matter. 



250 SCIENCE TEACHING 

Conceivable origin of life. Kelvin's views necessarily 
rejected: he merely shifted the main question to another 
planet. Life may have arisen from non-living material when 
conditions differed widely from the conditions that obtain at 
present. From some colloidal carbonaceous slime, activated 
by ferments? from cyanogen? from simple carbohydrates which 
captured nitrogen from ammonia, and so led the way to amino- 
acids and thus to proteids? We can only speculate. Biologists 
are sometimes a little violent in their emphasis over this ques- 
tion, but they cannot do more than express an opinion. 

The Biologist's Genealogical Tree 

If the evolution of species be accepted as a fact, some kind 
of genealogical tree showing the descent of Primate from Pro- 
tozoan logically follows. The traditional method of phylogenetic 
research has led to the belief that each group of animals has been 
derived from one of the known lower groups. It is generally 
believed, for instance, that the Arthropods are derived from 
the Coelomates. But biologists arc now beginning to believe that 
the early ancestors of such large fundamentally isolated groups 
as the phyla, all originated far back in pre-Cambrian times. 

In constructing a genealogical table, all sorts of questions 
arise. For instance, were the Vertebrates descended from the 
Annelids or from the Arthropods? There is an obviously close 
relation amongst the three highly specialized groups, but all 
three may have been, and probably were, descended indepen- 
dently from a common ancestor. Even experts differ in opinion 
over such questions, for there is generally an element of doubt 
about the evidence: some facts seem to point in one direction 
and some in another. Still, the experts are in agreement about 
the general genealogical sequence. 

For instance, if we consider the early Metazoa, the Ccelen- 
terates are obviously lower down the scale than the Ccelomates, 
for they have only a single gastro-vascular cavity, and no 
anus, whereas the Ccelomates have developed further, having 
both a body cavity and an intestinal cavity. 



EVOLUTION 251 

If the pupil's knowledge of zoology includes a knowledge 
of the essential differentiae between the phyla, he ought to 
be able to appreciate the following table. In fact he should 
memorize it. The main stem from Protist to man is easily 
recognizable in the main vertical column. Some of the branches 
are scarcely less interesting, if only because they include some 
of the complete phyla. (The phyla are shown in clarendon 
type.) 

Protista 
I 



Protozoa Plants 

I 



Ccelenterates Sponges 



111 I 

Flat-worms Coelomates Jelly-fish Sea-anemones and Corals 



I 1 1 i I 

Echlnoderms VERTEBRATA Molluscs Annelids Arthropods 



1 I. 

Cyclostomes Amphioxus 

Fishes 

I 

Amphibians 



Reptiles 

I 



ill! I 

Snakes Birds Mammals Crocodiles Tortoises and Turtles 
I 



Marsupials Placentals Monotremes 



Car- Whales Ungulates Insecti- Primates Bats Rodents Edentates 

nivores vores | 

I i 

Anthropoids Monkeys 

I 1 

MAN Great Apes 

The following tables are useful supplements to the genea- 

(E72) 18 



252 



SCIENCE TEACHING 



logical tree. The pupil should check them as far as his know- 
ledge of zoology permits. 



Evolutionary Stages. 



Representative Animals. 



No formed nucleus. 

Nucleated cell. 

Cell organs. 

Mouth. 

Nerve-ring. 

Central nervous system. 

Coelome, elaboration of heart. 

Primitive head. 

Elaboration of brain and head. 
Terrestrial life in moist places. 
Terrestrial life fully developed. 

Elaboration of instincts. 
Associative memory; warm 

blood. 

Evolution of intelligence. 
Reason, speech, use of tools 

and fire. 



Bacteria. 

Amoeba. 

Vorticella. 

Hydra, sea-anemone, corals. 

Jelly-fish, siphonophora. 

Flat- worm, tape-worm. 

Echinoderms, bivalve molluscs, 
earth-worms. 

Primitive molluscs, lower arthro- 
pods. 

Molluscs, fish, higher Crustacea. 

Land molluscs, amphibia. 

Many insects and arachnids, rep- 
tiles. 

Higher insects, spiders. 

Birds, mammals, higher reptiles. 

Higher primates. 
Man. 



Phylum. 


Nu- 
cleated 
Cells. 


Diges- 
tive 
Cavity. 


Body 

Cavity. 


Back- 
bone 
and 
Head. 


Jaws 
and 
Paired 
Limbs. 


Bone. 


Ter- 
restrial 
Life. 


Am- 
nion. 


Tem- 
perature 
Regu- 
lation. 


Protozoa 


X 


















Coelenterata 


X 


X 
















Coelomata . . 


X 


X 


X 














Cyclostomes 


X 


X 


X 


X 












Cartilaginous^ 

ft i 


X 


X 


X 


X 


X 










fish J 




















Bony fish 


X 


X 


X 


X 


X 


X 








Amphibians 


X 


X 


X 


X 


X 


X 


X 






Reptiles 


X 


X . 


X 


X 


X 


X 


X 


X 




Birds and | 
Mammals J 


X 


X 


X 


X 


X 


X 


X 


X 


X 



GEOLOGY AND PALEONTOLOGY 253 

CHAPTER XXII 

Geology and Palaeontology 

The Geology Commonly Taught 

It is unlikely that geology will become a substantive subject 
of science in schools, if only because of the difficulty of devising 
a suitable course of practical work. And yet no branch of 
science lends itself more readily to inductive treatment. In 
fact, practically the whole subject has been worked out by 
inductive methods. There is really no other way. And the 
subject has been placed on such a firm basis that it is to be 
regretted it is not given greater prominence in the school 
curriculum. 

Geology is essential for the full understanding of both 
geography and biology, and, in point of fact, certain elementary 
sections of the subject are almost universally included in all 
school courses of physical geography. For instance: 

1. The earth as a member of the solar system; form, size, 
movements. 

2. Material of the earth's crust; probable condition of the 
interior. 

3. Work of air, rain, rivers, oceans, ice, glaciers. 

4. Denudation, disintegration, transport, deposition. 

5. Rock-building by sediments. 

6. Volcanoes and earthquakes; earth movements, heat and 

lateral pressure, secular upheavals and depressions. 

Further work sometimes, but not very often, included: 

i. Architecture of the earth's crust: stratification, forms of 
bedding, alternations of strata, overlap, lapse of time 
represented by strata, groups of strata, order of 
superposition, joints, inclination of rocks, curvature, 
cleavage, dislocation. 



254 SCIENCE TEACHING 

2. Lessons from the Great Barrier Reef, and the shallow 

waters off Queensland. 

3. Rocks and minerals. Properties of minerals crystalline 

form, hardness, specific gravity, cleavage, lustre, 
colour. Classification. 

4. Sedimentary rocks and their classification. Softness or 

hardness of a rock no criterion of its geological age. 

5. Volcanic rocks and plutonic rocks. Compression. Moun- 

tain building. 

6. Geological maps. 

7. Evolution of the earth itself. Failure of the nebular 

hypothesis because of the resulting unsatisfactory dis- 
tribution of energy in the solar system. The meteorite- 
aggregation hypothesis. The sun-bolt hypothesis. 

8. The figure of the earth as determined by variation in 

gravity over its surface; the rigidity of the earth; 
methods of estimating time that has elapsed since 
final consolidation of earth's crust (io 9 to io 10 years 
by radio-activity calculation). 

I have seen some useful outdoor work done in quarry and 
in railway cutting, the pupil being provided with hammer, 
chisel, knife, magnet, lens, and (for testing carbonates) a small 
bottle of HC1. I have also been present on one or two useful 
geological excursions, once in a very successful hunt for 
microzoa amongst the shale of a disused quarry. Indoor work 
is necessarily largely of the museum type; the enthusiastic 
boy likes it, the average boy does not, and it is seldom of very 
great value. A certain amount of chemical analysis is possible, 
though it seldom leads far. The cutting of rock-sections for 
the microscope is beyond boys' skill. On one occasion I saw- 
two boys ploughing their way through Bauerman's two books 
on mineralogy, and not only had they become quite expert 
in the use of the goniometer, but they had made, from prepared 
cardboard " nets ", some excellent models of crystals. But 
such work does not take boys to the heart of the subject, and 
I am sceptical of its value. 



GEOLOGY AND PALAEONTOLOGY 255 



Why Some Knowledge of Palaeontology is Necessary 

One reason, perhaps the main reason, for including geology 
in a school science course is because of the paramount impor- 
tance of palaeontology in the teaching of biology. But palae- 
ontology is very rarely taken up seriously in schools. For its 
proper understanding, a preliminary treatment of most of the 
geological topics mentioned in the last section is desirable. In 
particular, a study of stratification, in some little detail, should 
be included. Pupils should be familiar with the accepted ter- 
minology the main geological time-division " Era " with its 
subdivision into " Periods ", and the further subdivision into 
" Epochs ", and the respective corresponding terms for geo- 
logical strata, " Groups ", " Systems ", and " Series ", though 
41 epochs " and " series " will seldom be mentioned unless the 
subject is taken beyond an elementary stage. There should 
also be included estimates of the age of the earth in geological 
time, and of the thickness of successive deposits; also how 
these estimates were made, and why geologists and physicists 
are much more nearly in agreement now than they were fifty 
years ago. 

The following topics might be included, but unless the 
learner is familiar with a fair number of typical living zoological 
forms, his study of palaeontology is likely to be very un- 
profitable. 



Suggested Topics for Inclusion in a School Course 

1. What Paleontology is. Reasons for concluding that 
fossil forms are relics of animals or plants which were once 
alive. 

2. The Eighteenth-century Discovery that each system of 
sedimentary rocks contains a definite assemblage of fossils, 
some of which are characteristic of that system. 



256 SCIENCE TEACHING 

3. How a Stratum may be traced across a country by means 
of its characteristic fossils. 

4. Evolutionary Advance. The obviously graded develop- 
ment of animal forms in the successive strata from the older 
below to the newer above. Only in the newer rocks is there 
any evidence of the highest group of animals the mammals. 
The vast thicknesses of the earlier strata containing only 
invertebrate animals; then the appearance of fishes, then of 
amphibians, then of reptiles and birds, then of mammals. 

5. Extinct Species: their position in the record. 

6. Conditions of Entombment. To be entombed and become 
a fossil, an animal or plant must (i) possess a skeleton, and (2) 
be covered up by a deposit. Since there are few places on land 
where material is being deposited to any large extent, terrestrial 
animals have relatively little chance of being preserved. The 
fossil remains of marine life are by far the most valuable. 

7. The Varying Composition of the Fossil Skeleton: chitin, 
silica, carbonate and phosphate of lime, calcite and aragonite, 
woody or corky tissues. Hence some are more readily pre- 
served than others. How and why some skeletons disappear 
and others are preserved. 

8. The Conditions in which Fossils Occur. (i) The entire 
original organism, e.g. the woolly rhinoceros and the mammoth 
frozen in mud and ice; insects and plants in fossil resin (amber), 
(ii) The skeleton alone, the organic matter being lost, as in 
certain shells in the pliocene beds, (iii) The original matter 
carbonized, as in some plants and some animals with chitinous 
skeletons, such as graptolites. (iv) A mould of the skeleton 
formed, the skeleton proper disappearing, especially when this 
consists of aragonite; water charged with carbon dioxide carries 
off the skeleton, (v) Petrifaction: original material replaced by 
another material, (vi) Imprints: no part of the animal itself. 



GEOLOGY AND PALEONTOLOGY 257 

9. uses of Fossils. (i) Fossils afford evidence of conditions 
under which the containing rocks were deposited, e.g. a deposit 
may be marine, or one formed in fresh water, or on land, (ii) 
Evidence of the climate of the period of deposit, (iii) The depth 
of the sea in which a stratum was deposited may be estimated 
when the fossils are represented by living specimens, (iv) 
Chronological value: once the order of successive formations 
has been determined, the characteristic fossil of a stratum en- 
ables us to refer any newly discovered formation to its proper 
place in the geological record, (v) Fossils often represent the 
ancestors of modern species, (vi) The fossils of animals which 
have become extinct (e.g. Graptolites, Trilobites) throw light 
on the relationship of existing animals and plants; in some 
cases, ancient forms are obvious links between now quite dis- 
tinct groups, (vii) Evolutionary evidence: by the study of the 
stratigraphical succession of fossil forms, the phylogeny (race- 
history) of animals and plants can be traced with certainty. 
Many of the classes and some of the orders of most of the 
great phyla of animals are found in the very early strata, and 
most of them in the Cambrian; but each is represented by its 
most rudimentary genera. Progress from one geological system 
to another from below is obvious. It is often easy to note the 
time of appearance of each great group; the Mezosoic mammals, 
for instance, are all marsupials, and not until Tertiary times do 
placentals appear; none but animals without a backbone have 
ever been found in the oldest fossiliferous rocks; fishes have 
obviously flourished long before any lung-breathing backboned 
animals; the cold-blooded amphibians and reptiles appear, 
successively, before the warm-blooded birds and mammals; 
man appears at the end. Linking forms may often be noted: 
reptile-like birds, bird-like reptiles, amphibians with affinities 
to fish, fish with affinities to the amphibians, tapirs with affinities 
to horses, forms intermediate between camels and llamas, and 
so on, all invaluable facts for determining ancestral lines. 

10. Difficulties about the Evolutionary Hypothesis. (i) Some 
forms have survived without change from very early times, e.g. 



258 SCIENCE TEACHING 

lingula from Cambrian times, and some 
Jurassic and Cretaceous times, (ii) There is very little evidence 
of the actual origin of the great phyla of the animal and plant 
kingdom; most of them seem to have appeared very suddenly, 
(iii) There is a general absence of transitional forms amongst 
plants; ferns, equisetums, and lycopods appear as far back 
as the Old Red Sandstone, in even more complex structures 
than their living descendants. The oldest known dicotyledons 
are those of cretaceous formation; they contain in the same 
deposit representations of the three great divisions, apetalous, 
monopetalous, and polypetalous. The general inference is 
that the geological records are very imperfect. 

11. Examples of Undoubted Lineage. There are well-known 
instances of undoubted intermediate forms between distinct 
species: (i) the series of fossil horses extending from the Eocene 
to the Pliocene, obtained from the rocks of the American 
continent; the evolution of the skeletal peculiarities of the 
modern horse strike the eye at once; (ii) the evolution of the 
camel: the skeletal development is again easily seen; study the 
consolidation of the bones of the foot, and the reduction in 
the number of incisor and pre-molar teeth; (iii) the freshwater 
snail Paludina. In all three cases, first show the pupils the 
youngest and the oldest forms, which will certainly convey 
the impression of distinct species; then put in position all the 
intermediate forms, and the evolutionary development is so 
obvious as to be impressive. 

12. Select a few type fossils characteristic of each system, 
and arrange them in chronological order. Invertebrates do not 
so readily tell their own story as vertebrates do, but a wealth 
of suggestive material is described in Mr. Henry Wood's 
Invertebrate Paleontology. 

* For figures of the evolving horse, camel, and elephant, see Lull's Organic 
Ei>olntion, pp. 577-640; for the snail series, see Haldane and Huxley's Animal 
Biology, or Lull's Organic Evolution', an evolutionary succession of 17 forms is 
given in both cases. Plate IV of Lull's book shows skeletons of horse and man side 
by side, with the corresponding bones marked; model skeletons themselves may be 
seen in one of the bays off the main hall of the Natural History Museum. The 
corresponding bones are all accurately named, and the close relationship of the 
mammals so apparently wide apart is seen at once. 



GEOLOGY AND PALAEONTOLOGY 259 

13. rupils should know that the whole succession of marine 
fossil-bearing rocks in Western Europe the most favourable re- 
gion in the world had been clearly ascertained before the idea of 
organic evolution was accepted by geologists. It was only after 
the publication of Darwin's work in 1859 that the meaning of the 
order in which fossils were known to occur became evident. 

14. Let each pupil make out, in " gridiron " form, his 
own tabulated stratigraphical chart, say with six vertical col- 
umns, these being headed (i) Eras (groups); (ii) Periods 
(systems); (iii) Thickness of sedimentary rocks laid down (in 
miles); (iv) Estimated age (in years); (v) Typical rocks; (vi) 
Typical fossils. The chart should not be overloaded; let it 
contain what can be remembered. Many boys will already 
have learnt from their geography such well-known rocks as 
the London clay in the Eocene period, chalk in the Cretaceous 
period, coal and ironstone in the Carboniferous period, sand- 
stone in the Devonian, slates in the Cambrian, and gneisses 
and schists in the pre-Cambrian. As regards fossils, the great 
thing is to note when each new phylum of animals appeared, 
or any noteworthy intermediate forms (e.g. archasopteryx and 
pterodactyls in the Jurassic, and intermediate mammal forms 
in the Eocene), or forms which have disappeared altogether 
(e.g. Graptolites in the Silurian, and Trilobites in the Permian); 
in short, any main facts supporting the evolutionary hypothesis. 
The appearance of the dicotyledons and of the large cryptogams in 
the carboniferous period should also be noted , though animal forms 
will, for the present purpose, naturally receive first attention. 

The chart should be so constructed as to give maximum 
help to the eye. For instance, since the total thickness of the 
rocks laid down is about 40 miles, the 40 miles might be 
represented by 5 inches, i.e. on a scale of 8 miles to the inch. 
Hence the 5 miles of thickness of the carboniferous system 
would be allotted a space across the chart of | inch, the 3 
miles of the cretaceous, f inch; and so on.* And all the 

* Alternatively, scale to time, instead of to thickness of deposit. The two scales 
do not by any means corresponds. 



260 



SCIENCE TEACHING 



selected type fossils should be sketched, no matter how roughly. 
But let the selection be small, and let it be learnt. 

15. Let the pupils construct a separate chart on a larger 
scale, showing the divisions of the post-Tertiary Era, with 
the Pleistocene and Recent Periods (with the Great Ice Age, 
and the Palaeolithic, Neolithic, and Bronze Ages); the Glacial, 
Palaeolithic, and more recent deposits, with their human relics; 
fossils of the great mammals now extinct (mammoth, &c.), and 
human remains. Impress on the pupils that all estimates as 
to thickness and ages of deposits must be received with great 
caution; they are at best only very rough approximations. 

Simpler and differentiated tabular schemes may be preferred. 
We append one or two. But encourage boys to prepare their 
own tabular schemes. Scaled " gridiron " schemes are always 
to be preferred. 

The first table shows the geological eras and periods, with 
respective time estimates. 



Rough Esti- 
mates of Time 


Era. 


Period. 


Age. 


Rocks. 


in Years. 










1 ,000,000 


Post-Tertiary 


Pleistocene, &c. 


Man 




60,000,000 


Cainozoic 


Pliocene, &c. 


Mammals 








Cretaceous 






2OO,OOO,OOO 


Mesozoic 


Jurassic 


Reptiles 








Triassic 














Mainly 






Permian 




sedimentary 






Carboni- 


Amphibians 








ferous 






4OO,OOO,OOO 


Palaeozoic 


Devonian 


Fishes 








Silurian 










Ordovician 


Invertebrates 








Cambrian 












Evolution of 




400,000,000 
(probably 
much longer) 


Pre-Cambrian 


Proterozoic 
Archeozoic 


Invertebrates 

Evolution of 
Unicellular 


Mainly meta- 
morphosed; 
igneous pre- 
dominant 








Life 





GEOLOGY AND PALAEONTOLOGY 



261 



The first column cannot be shown accurately to scale, as the 
1,000,000 years estimated for the age of man is less than 
i /iooo of the estimated time that has elapsed since the beginning 
of the evolution of unicellular life. 

The second table shows in a larger scale the 1,000,000 years 
estimated to represent the age of man, the post-Tertiary era. 
The first 100,000 years are not to scale. It is perhaps 5000 



Years Back. 


Period. 


Epoch and Age. 


Remains of 
Man. 






Historic 


Iron 


Modern 
man 


Bronze 


5,000 
IO,OOO 


Recent 


Pt-a 




Neolithic 








1 re- 
historic 




(Unknown) 






I OO,OOO 










Magdale"nien 


Cro-magnon 














man 


20O,OOO 












(true man) 












Solutre"en 




300,000 












Numerous 












Aurignacian 


remains of 














prehistoric 


4OO,OOO 






Stone 


Palaeolithic 




man found 














from these 














ages; also 


50O,OOO 


Pleistocene 






MousteYien 


of their 




or Glacial 








rough im- 














plements. 


6OO,OOO 














7OO,OOO 










Acheulen 




800,000 
























Chelle'en 




900 ooo 








PEolithic 




Eoliths may 


1,000,000 












be of human 














origin. 



262 



SCIENCE TEACHING 



years since the Bronze Age, and 8000 or 10,000 since the 
Neolithic Age. Between the Neolithic and Palaeolithic Ages 
there was a transition period probably extending over many 
tens of thousands of years, about which we know nothing. 

Here is another suggestive table, modified from Haldane 
and Huxley,* with which pupils should familiarize themselves: 



I 



.5 E 



* 1 

b rt * 

a 2 2 



Agre of Man 


Post Tertiary 


Recent 
Pleistocene 




















Pliocene 
















AKC of 
Mammals 


Cainozoic 


Miocene 
Oligrocene 












) 


7 






Eocene 














/ 






Cretaceous 














( 


Ajyo of 
Reptiles 


Mesozoic 


Jurassic 






' 




^ > 


k y 








Triassic 
















Age of 

Amphibians 




Permian 










r 


>-J 








Carboniferous 


t 


\ / 












Ajje of Fishes 


Palaeozoic 


Devonian 






r 














Silurian 
















Afire of 
Invertebrates 




Ordovician 




) 
















Cambrian 


> 















* The pupil should see the table in its original form, with its aids for visualization. 



GEOLOGY AND PALAEONTOLOGY 



263 



Lastly, a table showing the approximate thickness (in miles) 
of geological deposits: 



Recent and Pleistocene 


i 


I 


Post-Tertiary 


Pliocene 


i 


8 


Cainozoic 


Miocene 


2 


Oligocene 


*i 


Eocene 


zi 


Cretaceous 


3 


7 


Mesozoic 


Jurassic 


1 1 


Trias 


*\ 


Permian 


2* 


22 


Palaeozoic 


Carboniferous 


5 


Devonian 


4* 


Silurian 


3 


Ordovician 


3i 


Cambrian 


3J 



264 SCIENCE TEACHING 

The Descent of Man 

The pupil should be taught to sift carefully the evidence 
advanced concerning the history of man since his emergence 
from lower Primate stock a million years ago. Some such scheme 
as the second of the above tables should be provided, if only to 
show the pupil the enormous length of primitive palaeolithic 
culture, when primitive man was slowly struggling upwards. 
The duration of the subsequent cultures (neolithic, bronze, 
iron, present-day) are by comparison insignificant. Although 
man emerged from lower stock probably a million years ago, 
he was still semibarbarian as recently as 10,000 years ago, 
though his external appearance even 30,000 or 40,000 years 
ago differed hardly at all from that of man at the present day. 
An examination of pre-dynastic Egyptian mummies shows that 
types have certainly not appreciably changed in 10,000 years, 
but man has had a hundred times 10,000 years in which to 
reach his present state since his rationality dawned. 

It may be well to give the pupils some of the chief reasons 
for believing that man is of anthropoid origin. 

1. The blood of man and that of the great anthropoid apes 
give almost the same reactions. (It has been definitely estab- 
lished that the affinity of one species of animal to another may 
be determined by comparing the reactions of their blood.) 

2. The living anthropoid body possesses about the same 
susceptibility to infection as does the body of man. 

3 . The brains of man and the anthropoid are almost identical 
in their structural organization. The only real distinction is a 
quantitative one. 

4. The very complex structures connecting the human 
embryo with the maternal uterus are found in the anthropoid 
uterus, and in no other. 

5. The same vestigial structures occur in the bodies of 
man and anthropoid. 

6. The anthropoid mother fondles, nurses, and suckles her 
young in the human manner. 



GEOLOGY AND PALEONTOLOGY 265 

x i.wm:ology points to certain definite conclusions, and 
these the pupils should know. Homo sapiens, the species to 
which belong all the living races, and with almost equal cer- 
tainty all the races of which we have historical knowledge, is 
not the unique member of the human family. Four or five 
other kinds of man, sufficiently distinct to be placed not only 
in different species but in different genera, have existed in the 
past. They differed in the capacity of their skulls, in their jaws, 
in the curve of their backbone, and in their gait. The brain of 
Pithecanthropus , the most ancient of the fossils, was almost half- 
way in weight between the weights of the lowest living Aus- 
tralian and the gorilla; the brain of Piltdown man, the next 
in order of time, was larger, but still small, and these tw r o brains 
were defective in the regions concerned with speech and with 
the higher functions of the mind. On the other hand, the 
brain of Neanderthal man, although curiously shaped, was 
large, and the association of the fossils of this race in many 
parts of the world with flint instruments and a peculiar type 
of grave showed that its members probably had a definite 
culture and some kind of religious belief. 

The fossil evidence proves that there has been a process 
of evolution, but it is not sufficient to establish exact pedigrees: 
impress this on the pupils' minds. We do not know what 
were the characters of our own ancestors in the Pleistocene 
Age, or whether any of the other kinds of men were (so to speak) 
our grandparents or our great-uncles. 

The science teacher should exercise great caution in dealing 
with the history of primitive man. Some of the popular books 
are seriously misleading. One or more standard works should 
be consulted. Dr. G. G. McCurdy's Human Origins and 
Professor Osborn's Men of the Old Stone Age may be sug- 
gested. 

Palaeontology should be taught with the main purpose of 
providing the pupils with evidence clearly understood and 
convincing in character of the story of evolution. Avoid un- 
necessary details. Select the most telling facts. Make the 
reasoning cogent. Do not hesitate to point out doubts and 



266 SCIENCE TEACHING 

difficulties, to say outright that many things are not yet proven, 
that all our time-estimates are possibly a long way out, and that 
the whole hypothesis may break down, though this is not 
probable. 



CHAPTER XXIII 

Bacteriology 

The Present Importance of the Subject 

A good way to begin this subject is to discuss the distinction 
between the " poisons " that do not multiply and those that 
do. The effect of a poison like arsenic or strychnine is limited 
to the size of the dose. If a dose just large enough to be fatal 
is given to a rat, we are not surprised to discover that the 
flesh of the dead rat is poisonous. But if the dead animal 
were cut in small pieces, nobody would expect to find that each 
little bit was poisonous enough to kill another rat. Yet it had 
been noticed for centuries that some kind of multiplication in 
the bulk of poison seemed to occur in the case of many con- 
tagious diseases, and the conception gradually grew up of a 
living contagium that could grow and multiply. Eventually, 
in the middle of the last century, the anthrax bacillus, now known 
to be the exciting cause of splenic fever, was seen in the blood 
of a sick animal, and that observation led to investigations which 
have gradually built up the whole subject of bacteriology. 

Very little practical work in bacteriology is possible in school 
science courses, but there is a considerable range of facts 
which should be in the possession of all educated persons and 
which therefore should be taught. Everybody ought to know 
something of the work of Lister, Pasteur, and Koch, and of 
the trend of modern research into preventive medicine. We 
suggest some headings, with a few running comments, for 
teaching purposes. 



BACTERIOLOGY 267 

1. Lister. One of the greatest discoverers in the sphere 
of preventive medicine. He did for the craft of surgery what 
John Hunter had done for its science. When he began his 
work, operations were few, owing to the danger of putrefaction 
in the wound, followed in almost all cases by death. Lister's 
chief interest the problem of the healing of wounds. How 
he showed that inflammation was a reaction of the tissues to 
a noxious stimulant from without. When Pasteur had proved 
that putrefaction was caused by minute organisms suspended 
in the air, a method of prevention at once occurred to Lister 
to apply to the wound some substance which would destroy 
the micro-organisms without injuring the body-tissues. Later , 
he devised a method by which the organisms might be de- 
stroyed before they had even entered the wound. He thus 
discovered the nature of wound diseases. 

" Antiseptic " and " aseptic " methods. Difference. No 
real clashing. 

The Lister Institute and its objects. 

The fierce controversy about Lister's work and the stupid 
scepticism of the medical profession. Use this as an illustra- 
tion, in the history of science, of the inevitable opposition to 
new truths. (Other instances: Harvey's work, Pasteur's work, 
and the work of certain men of the present day.) Lister worked 
on imperturbably, and ultimately revolutionized the practice of 
surgery. The main characteristic of the man a search for 
true facts, and a fearless disregard of accepted medical opinion. 

2. Pasteur investigated the role played by bacteria in various, 
familiar natural processes, such as putrefaction, decay, and fer- 
mentation. He demonstrated that putrefaction and decay were 
not fields for the " spontaneous generation " of life, but were 
manifestations of chemical disintegration due to the metabolic 
activities of micro-organisms engaged in satisfying their need of 
food\ also that fermentation was caused by the effort of living 
and growing yeast cells to satisfy their nutritional requirements. 
Pasteur was the real founder of the science of bacteriology. 
Lister and Tyndall acknowledged the tremendous change 

(K72) 19 



268 SCIENCE TEACHING 

wrought in all conceptions of disease through the work of 
Pasteur. 

By 1865, the more enlightened medical world had realized 
that Pasteur's discovery (that particular fermentations were 
produced by specific microbes) indicated the possible nature 
of the various contagia viva responsible for disease. It was 
appreciated that diseases breed true, as dogs and cats breed 
true, and that they did not arrive de novo, although their ulti- 
mate origin was as mysterious as the origin of species of higher 
animals or plants. 

3. Koch placed bacteriology on the firm scientific basis of 
an independent branch of biology. In 1876, he showed that 
a specific bacterium (R. anthracis) was the cause of anthrax 
or splenic fever in cattle. His success stimulated many investi- 
gators to research along the lines of the germ theory. In 1882 
he conferred great benefit upon practical workers in this field 
by his invention and application of solid culture media, a tech- 
nical device by which it became possible to isolate single species 
of bacteria and obtain them in pure culture. Great discoveries 
immediately followed upon this important technical improve- 
ment. 

4. Present- day Bacteriological Workers tend to specialize in 
one of two directions, (i) Pathologic bacteriology: considera- 
tions given chiefly to the effects produced upon the animal body 
by the presence of bacteria and their toxins, to the distribution 
of the germs within the body, and to the reactions brought about 
by bacterial invasions, (ii) Hygienic bacteriology: this deals 
more particularly with the channels by which bacteria leave 
the human body and pass into the outer world; with the mode, 
duration, and life of disease germs in water, soil, and air; and 
with the avenues by which these diseases are able again to 
approach and infect healthy individuals. A common meeting- 
ground is found in research on immunity. 

5. Making Cultures. In the early efforts to grow bacteria 



BACTERIOLOGY 269 

in liquid solutions, every drop swarmed with many different 
kinds. Then came the device of using a medium which would 
remain a solid jelly even at the right temperature for growth. 
A drop of the fluid containing bacteria was shaken up with 
this jelly while it was still liquid; the medium was then poured 
out on a plate where it set into a layer of jelly within which 
the scattered microbes were held fast. When growth took 
place, the plate became dotted with separate colonies, each 
the growth of a single bacterium. If the purity was not obtained 
by one culture, the process was repeated, infection being used 
from that colony which seemed most pure. It thus became 
possible to trace the visible characters of each species through 
their many phases, and to explore their physiological and patho- 
logical properties. 

6. The sources of our knowledge of the life-histories and the 
different types of bacteria. 

(i) From pure cultures. By this means bacteria which are 
the specific exciting causes of such diseases as cholera, 
typhoid fever, tetanus, diphtheria, tuberculosis, and 
plague, have been identified. 

(ii) Discovery of insects as disease-carriers. This has led to 
exact knowledge of the causes of such diseases as 
malaria and sleeping-sickness. In these cases, the 
microbes are animals, and multiply in the blood of 
their vertebrate host. A biting insect mosquito, fly, 
or tick in pursuit of its own food, accidentally absorbs 
and carries the microbe from one animal to another. 
It took a long time to ascertain with certainty this 
causal connexion, and progress was further delayed 
by the natural misconception that the biting fly carried 
the infection mechanically, as a dirty needle might 
carry it in surgery. What really happens in most 
cases is that the microbe goes through a necessary 
stage of its life-cycle in the body of the insect, each 
kind of parasite being able to fulfil its destiny only 
if it is absorbed by the right species of insect. 



270 SCIENCE TEACHING 

(iii) The use of the ultra-microscope. The object is placed 
on a dark stage, and a very strong beam of light is 
sent horizontally through it. By this means it has been 
possible to detect very minute and very transparent 
mobile organisms known as spirochaetes, which elude 
observation by ordinary microscopic methods. In 
the ultra-microscope, the twisting spirals become con- 
spicuous shining objects. By this means the exciting 
causes of yaws and other diseases, probably including 
yellow-fever, have been discovered. The use of sun- 
light in the ultra-microscope allows an object as 
small as 0-004 /^ to ^ e visible.* 

7. Bacteria as objects of study. 

(\) Bacteria are minute unicellular organisms, usually classed 
as plants rather than as animals. But they lack 
chlorophyll, and it is probable that they occupy an 
intermediate place between plants and animals. The 
general dimensions are from -05 ^ to 2/4, though some 
are smaller, so small as to elude detection. 

(ii) Morphology, &c. Each type has distinctive visible char- 
acters, such as size and shape. But they are subject 
to modification by food, temperature, and the nature 
of the surroundings. They may appear singly, in 
pairs, in fours, in chains, in clusters, in cubical 
masses, &c. The characteristic forms are spheres, 
short rods, long rods, filaments, commas, short spirals, 
long spirals, curves, &c. 

(iii) The naming of the principal forms. The three main 
forms are typified, respectively, by a ball (coccus or 
micrococcus), a rod (bacillus), and a spiral (spirillum). 
More bacilli are known than cocci, and more cocci 
than spirillae. 

(iv) Response to environment, &c. Growth and cell-divi- 

* The principle of the ultra-microscope is quite simple. See, for instance, Dr. 
Mellor's Modern Inorganic Chemistry, p. 143, &c. 



BACTERIOLOGY 271 

sion; spore formation; effects of physical and chemical 
agents temperature, light, moisture, oxygen supply, 
food supply. 

(v) Culture study. The use of cotton plugs; the need of 
scrupulous sterilizing; preparation of culture media 
(beef broth, gelatin, agar, &c.); methods of obtain- 
ing pure cultures; separation of bacterial species; 
thermal death-point of different bacteria and how 
determined; staining reactions. 

(vi) Work with the microscope. Examination of living bac- 
teria and of stained bacteria. 

8. Example of Bacteria. {i) Cocci: staphylococci (in boils), 
streptococci (in erysipelas), pneumococci (in pneumonia); (ii) 
bacilli: the anthrax bacillus, the diphtheria bacillus, the tubercle 
bacillus; (iii) spirillce: spirillum cholerae (in cholera). The 
number of known bacteria is very large, and they are known 
only to experts. 

9. Filter Passers. Certain micro-organisms, of which very 
little is known, are so minute that they pass through a filter. 
If a solution containing ordinary microbes be passed through 
a Pasteur filter, the organisms themselves are kept back; but 
in certain cases, including even those producing a malady as 
common as foot-and-mouth disease, the filtered virus retains 
not only its infectious character but its power of multiplication. 
In this way, the conception of a filter-passing microbe has 
arisen. A few of these are said to be visible under the higher 
powers of the microscope, and some observers certainly claim 
that they are visible with the ultra -microscope. Really, how- 
ever, the ultra-microscope has added very little to our know- 
ledge of them. It is believed that the unknown agents of measles 
and scarlet fever are amongst them. 

10. Toxins and Anti- toxins. Ptomains and toxins as 
poisonous metabolic products of bacteria: our limited know- 
ledge of them. The remarkable potency of bacterial toxins. 



272 SCIENCE TEACHING 

Toxins as analogues of enzymes: characteristic quality of a 
true toxin its ability to evoke the formation of a specific 
antibody, an anti-toxin, when it is injected into the body of a 
suitable animal species. The diphtheria bacillus as an example: 
it grows in the throat and liberates into the blood a poisonous 
protein which is particularly dangerous to the heart; this pro- 
tein is called diphtheria toxin. When ground-up dead diph- 
theria bacilli are injected into a horse, antitoxin is developed 
in the blood, and this will protect human beings against the 
toxin. Somehow, the anti-toxin puts the toxin out of action. 
But only a few bacteria kill in the rather simple way employed 
by the diphtheria bacillus; hence few diseases can be cured by 
anti-toxins. 

n. Theories of Disease. In ancient times, the causes of 
disease were looked upon as due to some sort of supernatural 
intervention. It did not seem to occur to the ancients to under- 
take a rational investigation. It was known to the Romans, 
for instance, and before them to the Egyptians, that sleeping 
under a canopeum afforded a large measure of protection against 
marsh fever; and, less than a century ago, physicians were 
still framing hypotheses to explain how it was that a net placed 
above the sleeper could hinder the access to him, or diminish 
the virulence, of the " miasma " which, ex hypothesi, produced 
the disease by rising from the ground. Before the time of 
Ross, nobody seemed to argue that the chief business of a 
mosquito net must be to exclude mosquitoes! 

In the Middle Ages, the old idea of supernatural causes 
gave place to the view that the cause must be sought in some 
natural phenomenon perhaps the deleterious changes in the 
air from miasms emanating from the soil, the effluvium given 
off by unburied bodies, and the like. There were also those 
who believed that telluric influences like earthquakes and 
floods, or celestial phenomena like eclipses and the conjunction 
of planets, were responsible. 

At the present day the germ theory of disease is universally 
accepted. The idea that disease might be contracted by con- 



BACTERIOLOGY 273 

tact with the sick was definitely established in the sixteenth 
century, though it was recognized that this did not explain all 
epidemic diseases. By degrees the doctrine of contagion clearly 
emerged, and the work of Schwann and others prepared the 
way for Pasteur. 

Examples of diseases caused by definitely discovered germs 
are diphtheria, tuberculosis, cholera, tetanus, Malta fever. 

Examples of anti-toxins discovered are that for diphtheria 
and that for tetanus. 

No specific micro-organisms have yet been discovered as 
causing scarlatina, measles, whooping cough, hay-fever, rheu- 
matic fever, chicken-pox, mumps, influenza, and the common 
cold, but the germ theory furnishes the most reasonable, con- 
sistent, and probable explanation of them all. But we are not 
quite sure that micro-organisms are the cause. There is ground 
for believing that influenza is spread by contact of man with 
man, but there is no curative treatment for it, and it remains 
a " cough-mixture " disease. Once a germ is discovered, a 
cure ought to come along rapidly. Although, however, the 
tubercle bacillus has been found, there is no known cure. 
As for measles, it is not even known how the disease spreads, 
though contact is suspected. 

12. Research Work. The successful research work in cer- 
tain cases is of great interest. Malarial fever is such a case. 
It was a long time before the discovery was made that the 
responsible organism found its way into the blood by the 
bite of the anopheles mosquito. This knowledge made it 
possible to attack the disease by draining the pools where the 
mosquitoes bred, and in other ways. (The mosquito requires 
for its development shallow pools of stagnant water, and is 
moreover compelled to come up to the surface of the water at 
frequent intervals. If the surface of the pools is covered with 
petroleum, the larvae are destroyed.) It also became known 
that quinine is a drug capable of killing the malaria parasite. 
Another interesting discovery is the part played by the rat 
flea in spreading the plague, though, so far, no specific drug 



274 SCIENCE TEACHING 

for plague has been found. Still another case is the Indian disease 
Kala Azar; the discovery that antimony is a specific drug is 
likely to lead to its complete disappearance. 

Research workers try to discover (i) how an epidemic 
disease is caused; (2) how it spreads; (3) how it may be pre- 
vented from spreading; (4) how, when a man is attacked, his 
disease may be treated as effectively as malaria is treated by 
quinine or Kala Azar by antimony. The " treatment of symp- 
toms " is unscientific, as every practitioner well knows. 

13. Bacteria Exclusive as to their Host. No microbe is 
known to be capable of producing disease in all animals. 
The power of a microbe to produce morbid effects depends 
on the nature of the host. The typhoid bacillus if swallowed 
by man may produce a mortal illness, but it has no effect on 
cattle. 

14. Immunity. Natural and acquired immunity; body re- 
sistance to diseases; the unbroken skin as a barrier to micro- 
organisms, but the moist mucous membrane favourable to 
multiplication; saliva is germicidal; so is HC1 in gastric juice, 
though swallowed germs may get into the intestine. 

15. Metchnikoffs Work. The phagocytes. 

1 6. Dissemination of disease. 

17. Special Cases of Interest. Small-pox and the history 
of vaccination; no specific micro-organism has been isolated 
in pure culture; the virus can pass through a Chamber land 
filter; the relation between small-pox and vaccinia (cowpox); 
vaccination a process of active immunization; germicidal 
action uncertain. Epidemic influenza (e.g. 1918); uncertain if 
common influenza between the pandemics is identical with 
the apparently more violent kind. Leprosy and the new remedy 
" alepol " (sodium hydrocarpate). 

1 8. Drugs and their Action. Antiseptics kill off bacteria in 



BACTERIOLOGY 275 

infected wounds; ancesthetics (give examples) allow the surgeon 
to operate painlessly (explain action); quinine poisons malarial 
parasites in the blood-stream; digitalis regulates the action of 
the heart; atropine\ morphia. Useless drugs; limitations of 
drugs; the popular confidence in " medicine ". " Cure " 
fallacies. 

19. Pests and Pest Controls. Natural and cultural controls; 
poison sprays; fumigants; insects as fruit pests and enemies 
of agriculture; disease carriers, especially common flies and 
rat fleas; scavengers and pollinators; bites of ants and mos- 
quitoes; stings of wasps and hornets. 

20. Disinfectants and Antiseptics: difference. Recognized 
procedure for disinfection. Sterilization. 

21. Influence of Bacteria on Human Welfare. Bacteria dis- 
integrate and destroy dead bodies, attack and kill other living 
organisms, and certain kinds modify profoundly the composi- 
tion of the soil. 

22. The Modern Fear of Germs: unreasonable, and based 
on inadequate knowledge. The healthy child resists the action 
of germs, and tends to develop an immunity to the diseases 
common to his native land. 

23. An Interesting Speculation. At some period slightly 
preceding or during the reigns of the twelve Caesars, the malaria- 
bearing mosquito first found a habitat in the Roman marshes. 
The malaria was not of a severe type, but during two or three 
centuries it gradually sapped the vitality of the virile Roman 
population. Does the comparative mildness of the infection 
account for the prolonged but progressive decline of the 
Romans? 



276 SCIENCE TEACHING 

CHAPTER XXIV 

Hygiene 

Hygiene as Taught Forty Years Ago 

Is hygiene rightly called " science ", or is it an art, or just 
a code of rules, or a number of " laws "? We often hear of 
the " laws of health ". What are they, and why are they called 
I aw si 

Forty or more years ago, the Science and Art Department * 
included a hygiene syllabus in their directory of science sub- 
jects in which examinations were held annually. As the years 
went on, modifications were introduced, but the substantive 
headings were: 

1. Elementary Human Physiology. 

2. Sanitary Engineering and Construction. 

3. Water: composition, properties, storage, distribution, puri- 
fication. 

4. Air: properties, impurities, humidity, ventilation. 

5. Food: diets. Putrefactive changes in foods. 

6. Soil. Drainage. Sites. 

7. Habitations. Construction, sanitation, heating, lighting. 

8. Removal of water and impurities. 

9. Personal hygiene. 

10. Clothing. 

n. Prevention of diseases. 
12. School hygiene. 

To the syllabus was added a note to the effect that " it is impor- 
tant that the teaching of hygiene should be illustrated by 
practical demonstrations carried out in the class ", and suit- 
able experiments were suggested. Note that the teaching was 
to be illustrated by experiments, not base don them. Apparently 
the teaching was intended to be deductive, not inductive; 

This Department, which was responsible for such higher education as came 
under the review of the Government, and the " Education Department", which 
took cognizance of elementary education, were merged by the Board of Education 
Act, 1899. 



HYGIENE 277 

experiments were for verification, not for establishing prin- 
ciples. There is a further note: " For the elucidation of the 
topics covered by the foregoing syllabus, the following sug- 
gestions are made for practical demonstrations/* Here are 
three of the experiments: 

1. " Show the effects of respiration on air by (i) breathing 
on a slate, (ii) blowing into lime-water, (iii) blowing into a 
weak solution of Condy's fluid." 

2. " Weigh a dry brick; immerse it in water for half an 
hour, and weigh and note the amount of absorbed water." 

3. " Take a small quantity of solution of tannin and heat 
in a test-tube. In a second test-tube, dissolve a small quantity 
of isinglass in boiling water. Mix the contents of the two tubes. 
The white precipitate produced demonstrates the error of 
drinking strong tea when eating meat." 

Experiments of this type no doubt throw a small amount of 
light on principles laid down, though unkind people might say 
that the experiments tend to obscure the principles rather than 
illuminate them. In any case they are too trivial for a course 
of serious training in science. That is the trouble in treating 
hygiene as a branch of school science. The subject consists of 
such a multitude of different topics that a logically developed 
course of laboratory instruction rising year by year to higher 
levels of difficulty and development is scarcely possible. The 
very slightly related topics are all much of the same order of 
difficulty, except, of course, such a topic as food-study. 

It might be argued that to teach hygiene is to waste time, 
if only because most pupils have learnt from one source or 
another what they must do in order to keep fit: 

1. Obtain fresh air in abundance, breathe through the nose, 
practise deep breathing at regular intervals. 

2. Wear loose porous clothing. 

3. Eat and drink very moderately. Have no food fads, but see 
that the foods eaten contain the necessary vitamins. 

4. Let work, exercise, rest, and sleep be regular. 

5. Let all bodily habits be regular. 

6. Do not worry. 



278 SCIENCE TEACHING 

And yet the great majority of people violate one or more of 
these excellent rules every day. It is fairly safe to assert, for 
instance, that most people eat 50 per cent more food than 
good health demands, and that over-eating is the key to the 
large proportion of human ailments. It is interesting to observe 
that those who seem to know most about hygiene can seldom 
claim immunity from common diseases. 

That hygiene should be taught, everybody will agree, if 
only in order that the pupils may acquire a reasoned knowledge 
of its principles, for then they are much more likely to lay 
those principles to heart. But should the subject be taught 
as a branch of ordinary school science , or should facts and prin- 
ciples be dogmatically stated? 

The Kind of Teaching Advisable To-day 

Parts of the subject lend themselves reasonably well to 
laboratory treatment, but these are topics which are mainly 
direct applications of physics and chemistry. It is therefore 
wholly unnecessary to make special provision for the teaching 
of those topics as part of a course in hygiene as a special subject. 
For instance, the greater part of the necessary knowledge of 
the composition, properties, and purification of water and air 
is best given in the chemistry course; heating, lighting, water- 
storage and distribution, and matters concerning clothing, are 
best given as part of the physics course. These topics subserve 
the particularly useful purpose of illustrating principles laid 
down in the earlier parts of those subjects. In short, in the 
teaching of physics, chemistry, and biology, every opportunity 
should be taken to illustrate principles by reference to the 
laws of health. 

That done, the formal teaching of hygiene will be reduced 
to a few lessons of a summarizing nature. But unless biology 
is included as a substantive subject, a certain amount of human 
physiology and of bacteriology must be provided for. Here 
are some suggestions. First, in physiology: 

i. Structure and care of the teeth. The danger of decayed 



HYGIENE 279 

teeth. Pyorrhoea. The need of proper mastication. Saliva 
and ptyalin. The dental surgeon: his functions. 

2. The alimentary canal. Structure. Action of ptyalin, 
pepsin, and other ferments. Digestion and metabolism. 
Absorption. One important sign of good health an entire 
absence of a stomach sense. 

3. Diets. Chief foodstuffs. Ill-balanced diets. Seasonable 
diets. Relative digestibility of foods. Dangers of excessive 
eating. Sick-room feeding. Sugar not a natural food: too 
concentrated. Alcohol also too concentrated for welfare of 
body. Patent foods. Canned foods, dried foodstuffs, preserved 
vegetables. Overcooked foods. Hyperacidity, dyspepsia, con- 
stipation, diarrhoea. 

4. The heart. General notions of the vascular system. 
Mechanism of the circulation. The pulse and what it teaches 
Arterial schlerosis. Varicose veins. Anaemia. 

5. The respiratory system. The mechanism of respiration 
(this is rather difficult physics). Changes in the blood and in 
the pulmonary air. Composition of pure and expired air. 
Deep breathing. Nose breathing. Colds. Adenoids. Influenza; 
pneumonia; tuberculosis. Gas-poisoning. Principles of modern 
ventilation. 

6. The skin. General structure and functions. Cleanliness. 
Clothing. 

7. The muscular and nervous systems. Fallacy as to the 
advantage of great muscular development. Fatigue; sleep. 
Height and weight tables. Physical education. Neurasthenia- 
self-control . Stimulants . 

8. The surgeon and the physician: their respective func- 
tions. The terms " doctor ", apothecary, pharmacist, druggist, 
" chemist " (pharmaceutical and dispensing). Prescriptions. 

9. Drugs: their limitations. Patent medicines. 

Secondly, in bacteriology: 

i. The use of a nutrient gelatine. The presence of bacteria 
in the atmosphere; such bacteria unable to pass through plugs- 
of cotton-wool. 



280 SCIENCE TEACHING 

2. Demonstrate the presence of bacteria in water, in soil, 
and perhaps in milk. Show their absence from boiled water, 
boiled milk, and ignited soil. 

3. Examples of fermentation. Nature of ferments. Heat 
of fermentation due to the energy set free in the breaking down 
of the highly complex molecular structures into simpler com- 
pounds. 

4. Putrefaction and decay. Why things " go bad ". The 
possibilities of a dirty dish-cloth in a damp, warm, dark place. 

5. Harmless and useful bacteria. Injurious bacteria and 
the cause of disease. The prevention of contagion. 

6. The preservation of foods. Sterilization. 

7. Antiseptics, disinfectants, deodorants. The work of 
sunshine, dry heat, steam, boiling, fire, as agents of beneficent 
destruction. The home medicine-chest: how it should be 
stocked; the list of emergency instructions to be pasted inside. 

In short courses of this kind, playing a subsidiary role, 
little practical work will, as a rule, be possible. But for the 
physiology it would be useful to lay open a freshly chloroformed 
rabbit or guinea-pig, to show the relative positions of the internal 
organs; the alimentary canal is easily removed after examina- 
tion, and the heart, the main blood-vessels, and two or three 
principal nerves may then be exposed to view. 

The practical work attempted will depend on the training 
and experience of the teacher. If the subject has to be taught 
by, say, the teacher of physical training, no practical work is 
likely to be attempted, nor would it be desirable, for the courses 
in physiology at the physical training colleges are strictly 
elementary in character; not all the colleges have a biological 
laboratory. 

The non-specialist science teacher who teaches hygiene can 
hardly be expected to treat the subject effectively. And some- 
times he or she is sadly out of date, depending for the 
necessary facts on some small text-book written in the eighties, 
or perhaps earlier still. This applies even to a subject like 
ventilation. 



HYGIENE 281 



The Foundations of Hygiene 

However the subject of hygiene is taught, the great thing 
is to implant in the child's mind the all-important fact that 
the fundamental problem of health is the scientific nurture of 
the body. The best nurture of the body is simply a question 
of nutrition, and the elements of nutrition are: (i) food, (2) 
fresh air and sunlight, (3) bodily exercise, (4) warmth, (5) 
cleanliness, (6) rest. The loss of any one of these means inV 
pairment of health; the neglect of them is an invitation to 
disease. But they must all be followed in moderation. 

Another important thing is to " avoid all stunts and 
panaceas ". Tell the pupils that, if they are ever tempted to 
take a patent medicine, they should first read the British 
Medical Association books, Secret Remedies, in which they will 
find the analysis and the cost of all the patent medicines in 
the market. Why pay three shillings for a bottle of harmless 
mixture or pellets that can be made up for a penny? 

Personal talks to older pupils may take a great variety of 
useful forms. Amongst suitable topics are the local provision 
of a sanitary environment housing, water-supply, drainage and 
refuse removal, clean streets; infant welfare; child hygiene; 
a wholesome food-supply; the segregation of infectious persons, 
disinfection, quarantine; the production of immunity; the pro- 
vision of anti-toxins; attacks on epidemic diseases; clinics; 
sanatoria; hospitals; compulsion and education in public 
health work; preventive medicine. A knowledge of all these 
things is necessary for the creation of reasoned opinion in the 
interests of public health; and the Sixth Form boy or girl is 
easily made a future missionary. Whether the knowledge is 
given dogmatically or not, the important thing is to provide 
the knowledge. 

Briefly, the laws of hygiene rest on the principles of physics, 
chemistry, and biology. These principles known, there is 
little more to be done then to apply them, and, in the appli- 
cation, relatively little experimental work is necessary. If the 



282 SCIENCE TEACHING 

preliminary physics, chemistry, arid biology have not been 
done, hygiene should still be taught, but it will fail to make 
the same appeal, even if experiments are devised to illustrate 
and to elucidate the points taken up. 



CHAPTER XXV 

Biological By-ways 

Occasional Work for Abler Boys 

There is no time in school to wander far away from the 
beaten track, but the occasional enthusiast of the Sixth Form 
who leaps ahead of his fellows may be encouraged to read 
more widely than is demanded by any formal syllabus. Such 
boys might well be required to read Bell Pettigrew's Design in 
Nature and D'Arcy Thompson's Growth and Form, especially 
if they have a liking for mathematics. (The writer of the first 
book was, and the writer of the second book is, a distinguished 
Scottish professor.) The books teem with interest, even for 
the professional biologist. Professor Pettigrew's book (3 vols.) 
contains 2000 figures, many of them striking. The collection 
of facts is remarkable, but the writer's fault was that he was 
too dogmatic in the expression of his views. Professor D'Arcy 
Thompson's book (about 800 pages and 400 illustrations) is 
rather more recent, and is even more remarkable in some ways. 
The following points, amongst others, might receive attention, 

Special Points suggested for Consideration 

i . Structure and Size. If two bridges, geometrically similar, 
are of different sizes, the larger one is the weaker of the two: 
Why? Nature cannot construct animals beyond a certain 
size: Why? A man 60 feet tall would crush down with his own 
weight: Why? Big birds have great difficulty in flying: Why? 

In any structure which is enlarged without alteration of 



BIOLOGICAL BY-WAYS 283 

shape, the bulk increases as R 3 , but the surface only as R 2 . 
As the bulk of animals becomes greater, it becomes more and 
more necessary to provide greater and greater absorption sur- 
face in the intestines; hence new arrangements have to be 
made for making the surface more or less proportional to R 3 . 
In many animals the difficulty is surmounted by coiling the 
intestine; even in man, the intestine is three or four times as 
long as the whole body. 

2. A nimal Locomotion* Locomotion on land, in the water, 
and in the air. How the movements are effected. The wing 
as a helix. Feather arrangements. 

3. Organic Form, (a) Unduloids and Catenoids, and how 
developed geometrically. Minimal surfaces. Plateau 's experi- 
ments. Falling drops and splashes, hanging drops, breaking 
waves. Examples of such shapes in organic cup-like and other 
creatures, e.g. the vorticella, folliculina, and some of the for- 
aminifera. (b) The logarimithic spiral mathematically considered, 
exemplified in various organisms: nautilus, molluscan shells, 
the successive whorls of spiral shells, the spiral shells of the 
foraminifera, the horns of sheep and goats, the antlers of 
deer, the spiral arrangements in nature generally, spiral for- 
mations in plants, spiral stems, spiral distribution of leaves and 
branches, spiral climbing plants. Radiating, concentric, and 
spiral arrangements common to crystals, plants, and animals. 
(c) Hexagonal symmetry, (d) Phyllotaws. (e) Geometrical forms 
in corals, pollen-grains, spores, fish scales, scales of butterfly 
wings, &c. 

4. Comparison of Related Organic Forms and their geo- 
metrical transformations (e.g. skulls), shown graphically by 
deformations of co-ordinate networks. 

5. Sizes of Organic Forms. A typical bacillus is i ^ in 
length. One of the smallest known organisms is M. progrediens, 
a pathogenic micrococcus of the rabbit; diameter -00015 mm. 
(= -15 /z 1-5 X io~ 5 cm.). Filter-passers are, of course, 
smaller still. 

* In Nature for April 7, 1928, there is an interesting article by Mr. A. Mallock, 
F.R.S., on Some Modes of Mechanical and Animal Locomotion. 

( E 72 ) 20 



284 SCIENCE TEACHING 

The M. progrediens contain only about 30,000 molecules of 
albumin, i.e. 30 X io 3 . Hence an organism only iV the size 
would contain only about 30 molecules of albumin. Thus 
we begin to reach molecular dimensions, and there is appar- 
ently a limit to the smallness of organic size. This must be 
borne in mind when discussing hereditary factors (genes). 



CHAPTER XXVI 

Astronomy 

The Astronomy Usually Taught 

As a subject for serious study, astronomy is rarely included 
in a school science course, one reason being the difficulty of 
finding practical work of a suitable kind. But all geography 
courses contain a certain amount of elementary astronomy; 
for instance: 

1. The earth as a globe travelling round the sun and 
spinning all the time on its own axis inclined 66 1 to the plane 
of the ecliptic, i.e. the plane of its path round the sun. 

2. The consequences of these movements: day and night, 
the seasons. 

3. The moon as a globe spinning on its own axis once a 
month, and travelling round the earth once a month, in a plane 
slightly inclined to the plane of the ecliptic. Phases of the 
moon. 

4. Eclipses: comparative rarity of the phenomenon the 
result of the inclination of the orbits of the earth and moon. 

5. Fixing positions on the earth's surface. Latitude and 
longitude. Elementary notions of map projection. 

Older pupils who have done a fair amount of geometry, 
especially geometry of the sphere, have no difficulty in under- 
standing these things from descriptions and diagrams. But 
younger pupils require more help, otherwise they cannot visu- 



ASTRONOMY 285 

alize the phenomena, they remain puzzled, and their written 
answers to questions are seldom satisfactory. 

If an orrery is available, there is little difficulty, but more 
often than not, the teacher has to manage with improvised 
models, perhaps a mounted globe to represent the earth, and 
painted wooden balls to represent the sun and moon. Per- 
sonally I prefer to use a large porcelain globe (the kind used 
with the old-fashioned paraffin lamps) to represent the sun, 
the globe being fixed in position a foot or so above the centre 
of the table, and illuminated from the inside by the most 
powerful electric light available, the room being otherwise in 
darkness. This makes an admirable sun, and gives a sharply 
defined shadow. The earth may be represented by a small 
wooden ball painted white, with a knitting-needle thrust through 
its centre to represent the axis, and with black circles to repre- 
sent the equator and the 23 1 and 66 1 parallels, the ball being 
mounted so that its centre is the same height above the table 
as is the centre of the sun, and the axis being inclined at 66 J. 
About one-half the " earth " is now brilliantly illuminated, 
and the other half is in shade. If the earth is moved round 
in its orbit, the successive positions of its axis maintaining a 
constant parallelism, the meaning of (i) day and night and their 
varying length in different parts of the world, and (ii) the 
seasons, may be made clear in a few sentences. If more serious 
work is to be done later, it is particularly necessary that the 
plane of the ecliptic should be clearly visualized, and this is 
easily done if the sun and the earth are supposed to be half 
immersed in water, the surface of the water representing the 
plane of the ecliptic. Make the pupils see clearly that half the 
earth's equator is always above, and the other half alw r ays 
below, this plane. 

The phases of the moon are best taught by ignoring the 
model of the earth for the time being and considering models 
of the sun and moon alone. Let the laboratory sun illuminate a 
painted ball, to represent the moon; let the pupils move round 
this ball, from a position where they see the non-illuminated 
half to the position where they see the fully-illuminated half. 



286 SCIENCE TEACHING 

One " phase " after another comes into view, and further 
teaching is unnecessary. Now put the " earth " in position, 
and show how the earth may get between the sun and the 
moon, and prevent the sun from shining on the moon; and 
how the moon may get between the earth and the sun, and 
prevent our seeing the sun. And thus we come to eclipses. 

The first essential in teaching eclipses is to make pupils 
realize that a cone of shadow is a thing of three dimensions. 
Let the school sun cast the shadow of the much smaller school 
earth. The whole classroom remains brilliantly lighted save 
for a cone of darkness on the far side of the earth (we ignore 
all other objects in the room), and the shape and size of this 
cone is easily demonstrated by holding a screen at varying 
distances behind the earth. With a second ball to represent 
the moon, correct notions of total, annular, and partial eclipses 
may be readily given. It is quite easy to show why eclipses 
are comparatively rare phenomena by making the moon move 
round in an orbit inclined to the earth's orbit. 

But this is not all. It now remains to represent the sun, 
moon, and earth in proper proportion and at their proper 
relative distances. Only in that way are pupils likely to obtain 
a true sense of things. If the " sun " is 20 inches in diameter, 
the earth may be represented by a ball ?> inch in diameter, 
and the moon by another, v>V inch. It will pay to take three 
spheres of these respective sizes (say one of the old-fashioned 
geography " globes ", a small pea, and a grain of onion seed) 
and place the two former 20 feet apart, and the two latter 
6 inches apart. The true relative sizes and distances always 
impress the pupils. To cast the actual shadows of such small 
spheres is in practice impossible, of course, but by a little 
exaggerated geometry it is easy to show why the moon's shadow 
which swept across England during the solar eclipse of 1927 
was limited in width to about 15 miles. This earlier work must 
be devised to enable the pupils actually to picture the pheno- 
mena fairly accurately. Later work is then comparatively simple. 



ASTRONOMY 287 

A More Serious Course of Astronomy 

The main interest of astronomers is now concentrated on 
the stars and the possible organization of the universe as a 
whole. But in any serious school course of astronomy, at least 
the introductory work will be confined, in the main, to the solar 
system. The main topics are therefore likely to be: 

1. The sun and moon; their dimensions and distances. 

2. The planets and their satellites. Planetary distances. 

3. Comets and meteors. 

4. The apparent movements of the sun, stars, moon, planets. 
How we discover the real movements. 

5. Stars, nebulae, the Milky Way: elementary considerations. 
Names of well-known stars and of easily recognized constellations. 

6. The observatory and its instruments. How a combined altazi- 
muth and equatorial may be made for school use. 

7. Determination of apparent positions of the heavenly bodies. 

8. Determination of real distances and dimensions of the heavenly 
bodies. Possible deductions when one measurement has been de- 
termined. Analogy with terrestrial trigonometry, (i) Determination 
of circumference and diameter of the earth, (ii) Determination of 
distance of moon. 

9. Gravitation and Newton's discovery. Kepler's Laws. 

10. True shape of the earth. 

11. Greenwich and its time signals. Measurement of time. 

12. The nautical almanac: elementary considerations. 

Some of these topics are puzzling to many boys. For 
instance: 

i. Relative Motion. Devise means to make the boys see 
clearly that if they could make their observations from the 
relatively fixed body of the solar system, viz. the sun, there 
would be no confusion; that the confusion arises because they 
make their observations from a body which itself is moving. 
Show them that the ancients were fully justified in their de- 
scription of the epicycles, inasmuch as epicycles are exactly 
what we observe when, forgetting our own motion, we note 
the planetary paths amongst the stars. (We may make a series 
of observations and plot a portion of some particular planetary 
path for ourselves, but the work must extend over a long period.) 



288 SCIENCE TEACHING 

Devise a geometrical diagram or copy one from a standard 
work on astronomy to show that a looped path of a planet is 
merely the result of our watching the movements from another 
planet, which is pursuing a similar motion round the same 
central body. Another puzzling case is the path of the moon 
round the earth as the earth moves round the sun. A pencil 
stuck at right angles to the edge of a disc (a bread-board, a 
plate, or the cylinder from the art-room will do), and the disc 
rolled along the edge of the table which has been pushed up 
close to the wall, describes on the wall an epicycloidal path. 
If a circular cardboard disc, 2 or 3 inches greater in diameter 
than the base of the cylinder, be pinned centrally on the latter, 
and the pencil be stuck to its edge; and if the cylinder be rolled 
along the edge of the table so that the projecting edge of the 
disc is below the table-level, the pencil will trace out a looped 
epicycle on the wall. A similar sort of curve will be traced 
if the disc and cylinder be made to roll round a fixed cylinder. 
Experiments of this kind help greatly to show how the 
apparent complexity arises in the path traced out in space by 
members of the solar system. They are more convincing than 
curves drawn from geometrical data, and take up much less 
time. Some of the modern astronomy books contain suggestive 
diagrams, and these perhaps may be used instead. But mere 
words are useless to make pupils understand the complexity 
of motions within the solar system. 

2. Celestial Measurements. Diameters and distances. Once 
pupils realize that this work is very little more than a repetition 
of what they have done in trigonometry, there is little difficulty. 
It is generally a question of a base line and the measurement 
of angles, over again. The principle of determining a circum- 
ference of the earth by means of the zenith distances of a 
selected star from the two ends of a known base-line is easily 
understood by a Fifth Form boy; so also is the moon's distance 
by means of (what is practically) the Greenwich-Cape base- 
line. All other important measurements of the solar system 
follow on simply, and need take but little time. The main 
thing is to master main principles. 



ASTRONOMY 289 

The pupils must, of course, know something of the geo- 
metry of the sphere, and must see clearly the relation of the 
earth to the celestial sphere. In particular, they must be 
familiar with (i) the zenith and the horizon, or (2) the celestial 
pole and celestial equator. Let them understand that the 
earth's axis would, if extended, pass through the celestial poles, 
and that the earth's equator extended outward in its own 
plane would become the celestial equator. Also that, just as 
positions on the earth are determined by parallels of latitude 
and meridians of longitude, so positions on the celestial sphere 
are determined in exactly the same manner. The astronomer 
calls his parallels, parallels of declination, and his meridians, 
meridians of right ascension. Just as we say that our equator 
has a latitude of o, so the astronomer says that the celestial 
equator passes through all points (on the celestial sphere) of 
declination o. And just as we measure longitude from an 
arbitrarily chosen point on the equator (the point through 
which the Greenwich meridian passes and called o), so the 
astronomer measures his right ascension from an arbitrarily 
chosen point on the celestial equator, the first point of the 
constellation Aries. Jn short, we fix positions on the celestial 
sphere exactly as on the earth. This must be realized geo- 
metrically, and a rough model made, say, of wooden hoops 
will help the pupils much. 

A pupil might begin making celestial measurements by 
using his altazimuth, taking the altitude and azimuth of some 
selected stars; show him that these measurements are some- 
times made in order to define the position of a star in that 
portion of the celestial sphere we can see above our own 
horizon. Now show him how to alter his altazimuth so that 
its telescope is mounted equatorially, and show him how to 
take the declination and right ascension of the same star, these 
measurements fixing the position of the star independently of 
a particular person's horizon. 

All those things are the ABC of the whole subject. The 
celestial sphere and its relation to the earth must be visualized 
and understood before any headway can be made. The pupil 



290 SCIENCE TEACHING 

must see that the astronomer and the surveyor are engaged in 
-exactly the same kind of work they both measure base-lines 
and angles, they both use telescopes to see distant objects; 
but the astronomer's base-lines are much longer, his distant 
objects are very much farther away, and his telescopes are 
therefore much more powerful. 

Let the astronomer's refinements all be postponed until 
main principles are mastered. In the earlier work, do not 
trouble to average the distances of circumpolar stars, but look 
upon Polaris as a true polar star; also ignore verniers, refraction, 
aberration, precession of the equinoxes, obliquity of the ecliptic. 
Main principles first; refinements later. 

Practical Work 

What practical work can be done? In day schools, very 
little, if only because of the difficulty of getting boys back in 
the evening. Valuable work is possible in a boarding school, 
and it sometimes happens that a school astronomical society 
spends more time with the telescope than the school authorities 
approve. A good telescope is a first essential, and it is a great 
advantage if this can be mounted as an altazimuth which is 
convertible into an equatorial (by revolving the base about a 
horizontal axis). Unless the school is lucky enough to have an 
observatory, other astronomical instruments are hardly likely 
to be available, though of course a spectroscope will be part 
of the physics equipment. 

The kind of exercises easily possible are: observations of 
the moon and the planets, the recognition of the better-known 
constellations and of the well-known stars, the motion of the 
stars, the plotting of the moon's path amongst the stars, obser- 
vations of one or two planetary paths amongst the stars, identi- 
fication of a few of the great nebulae, determination of the 
meridian, determination of the latitude of the place by measur- 
ing the altitude of the pole star, simple determinations with 
the altazimuth and equatorial. 

One kind of exercise that always appeals to a boy is this: 



ASTRONOMY 291 

the latitude of two places approximately on the same meridian 
may be taken from an atlas, say, Glasgow and Plymouth, or 
St. Louis and New Orleans, the distance in miles between the 
places measured approximately from the atlas, and the circum- 
ference of the earth then calculated. 

Whatever can be done by observation and experiment to 
make the astronomy real, should be done. 

Sixth Form Work 

Certain aspects of astronomy, especially mathematical 
astronomy (the lunar theory, for instance) are beyond school 
boys; but there are aspects of present-day research that should 
be included in any Sixth Form course. 

This, in the main, is work in astrophysics, a region in which 
astronomy and physics overlap. Astrophysics may be regarded 
as the study of the light received from the celestial bodies, 
and of the consequential problems concerning the constitution 
and inter-relations of those bodies. The chief instruments 
used are the telescope, the spectroscope, the camera, and the 
interferometer. By long exposure, the camera can photograph 
objects too faintly illuminated to impress a plate in a short 
time; and, more than this, a photographic plate is sensitive to 
ultra-violet light which the eye cannot see. Since many of 
the new important spectra lie in the ultra-violet region, the 
interpretation of such spectra is almost entirely an affair of 
interpreting photographs. But this class of photography is of 
much too expert a character to be attempted in schools, and of 
course no school is likely to be equipped with an interferometer 
(an instrument for the direct determination of stellar distances). 

School work will probably be confined to the full under- 
standing of the working of the spectroscope, to consideration 
of the data which astronomers have obtained, and to the infer- 
ences that may be drawn from such data. We summarize a 
possible course. It is assumed that a course of light has already 
been done, also that the pupils have an elementary knowledge 
of the spectroscope. 



292 SCIENCE TEACHING 

1. The Spectroscope: 

(1) Its original use in chemical analysis. How it now 

provides us with a great wealth of physical data. 
How the spectroscope is influenced by changes in the 
chemical and physical condition of the object 
observed. 

(2) The two methods of analysis: (a) by glass prism, (b) 

by diffraction grating. Explanation, and elementary 
theory. 

(3) Three standard methods of exciting a substance to 

radiate its energy: (a) flame, (/?) arc, (y) spark. The 
enhanced lines of a spark spectrum and what they 
signify. 

(4) Emission and absorption spectra: the essential differ- 

ence. 

(5) Continuous, line, and band spectra, and how they are 

produced. 

(6) How and when a luminous vapour may give its spectrum 

either as light emission lines on a dark background, 
or as dark emission lines, in the same position, on 
a bright background. 

(7) Why luminous solids and liquids emit continuous 

spectra. 

(8) The remarkable regularity of spectrum lines, even when 

they appear to be hopelessly chaotic. 

2. The Principle of Spectrum Analysts. The wave-lengths 
of the spectrum lines produced by an unknown substance are 
measured, and are then compared with tables giving the wave- 
lengths of lines corresponding to the different chemical elements; 
the identification is then made. 

The direct measurement of wave-lengths is a very laborious 
matter. Standard wave-lengths have been measured with 
very great accuracy, especially the numerous lines of the 
iron arc spectrum; and the wave-lengths of unknown lines 
are calculated from the position of the lines with respect to 
the standard. Show how, in practice, the iron arc and the 



ASTRONOMY 293 

unknown substance are exposed to different portions of the 
slit, and how the rows of lines are thus compared. 

3. Displacement of Spectrum Lines: the causes. 

4. Radiation. This is the question of modern spectroscopy 
and astrophysics: what is actually taking place in the radiating 
body that results in the spectrum we see? Hypothesis: the 
smaller the orbit in which an electron revolves, the smaller 
the amount of energy possessed by the atom, so that, in the 
normal state, the atom has its minimum energy. The exciting 
agency, therefore, in removing the electron to a distant orbit, 
adds energy to the atom, and when the electron returns, the 
atom must give up some or all of this energy, according to the 
particular inner orbit in which the electron now revolves. 
It is precisely the energy which the atom thus yields up that is 
held to account for radiation. It is radiated in the form of an 
aetherial wave of a certain definite frequency. (See Chapter 
XXXI.) 

5. Wave-lengths and Frequencies. Special units are em- 
ployed, inasmuch as the magnitudes are so entirely different 
from those with which we are familiar, and it is therefore desir- 
able to deal with figures of reasonable dimensions. 

(i) Wave-length unit = io~ 10 metre 

-- i "tenth-metre" or "ANGSTROM UNIT 
(A.U.)." 

(ii) Frequency: not usually indicated by the number of waves 
sent out per second, but by the number of waves contained in one 
centimetre of the wave-train; this 

true frequency . 

= M __ __* wave number. 
velocity of light 

Let the pupils apply this principle to a particular instance, and 
let them memorize both the principle and the instance. Con- 
sider the wave-length of, say, a particular green colour, measured 
and found to be 0-0000005 metre. 



294 SCIENCE TEACHING 

Wave-length = 0-0000005 metre = 5000 A.U. 

Frequency = ^ loc l ty - of . light _ = 3 x I0 * ( metres P er second 
wave-length in metres 0-0000005 

= 6 x 10 14 waves per 
Hence, second. 

. I true frequency \ 6 X io 14 

wave-number ( -= - - f -------/-I = s 

\ velocity of light/ 3 X io 8 X io 2 

= 20,000. 

Thus the particular radiation has: 

(i) a wave-length of 5000 A.U. (usually written A5000 A.U.). 
(ii) a wave-number of 20,000 (usually written v20,000). 

Visible light extends from about A76oo in the red to A39OO in 
the violet. 

6. Solar Spectra. Photographs and how they are inter- 
preted. 

j. Stellar Spectra. Their interpretation. Questions to be 
answered: what physical conditions give rise to the spectra 
of the stars? and how are these conditions related to other 
stellar qualities? Some idea of the way in which stellar magni- 
tudes, movements, velocities, distances, temperatures, and colours 
are interred. 



Topics for Lectures 

In school astronomy, there are certain topics which are best 
treated frankly as lectures. They concern the results of recent 
research. The results are easily described, and much of the 
supporting evidence may easily be understood by Sixth Form 
boys. All through the lectures, facts should be carefully 
distinguished from hypotheses, and an endeavour should be 
made to indicate the degree of probability of the truth of each 
hypothesis, according to the extent and nature of the evidence 
on which the hypothesis rests. 

i. The Stellar System. Number of stars: 5000 visible to 



ASTRONOMY 295 

naked eye, 100,000 in a i-inch telescope; perhaps about 
1,500,000,000 in all. Our sun not far from centre of stellar 
system. System apparently finite: its general shape. Stellar 
distances: nearest star is Prox. Centauri, (24 X io 12 ) miles 
distant; then a Centauri, (25 X io 12 ) miles; then Lalande, 
(47 x io 12 ). Sirius, the brightest star in the sky, is (50 X io 12 ) 
miles away. There is a steady succession of objects until 
20,000 times the distance of Sirius is reached. One known 
star-cluster is (6 X io 18 ) miles distant. 

It is useful to convert these vast distances into light years. - 
Light travels at 186,000 miles a second, i.e. at 6 billion (6 x io 12 ) 
miles a year; this distance, (6 x io 12 ) miles, is called a light year. 
Thus the nearest star is about 4 light years distant, and some 
of the remoter nebulae may be a million light years (6 x io 18 
miles) distant. 

Stars do not interfere with one another much. Each has 
as much space to move about in as one tiny midge would have 
in the largest hall in the world. We do not know how many 
extinct (dark) stars exist, but dynamics suggest not more than 
ten times the number of luminous stars. Estimated that a 
star would suffer collision only once in io 14 years. 

Stellar system recognized as one vast organization, pointing 
to a common origin of large groups of stars; for instance, the 
bright stars of Orion have a common motion; so have the 
Hyades . 

2. Size of Stars. In 1920, Michelson measured the angular 
diameter of Betelgeuse (the first time a star was thus measured), 
a 2O-foot interferometer being used. The star had a disc a V 
of a second of arc in diameter, the size of a halfpenny fifty miles 
away. The distance being approximately known, this apparent 
size can be converted into approximately the actual size. 
Diameter = 200,000,000 miles. 

The older method of estimating the sizes of stars: From 
our knowledge of a starts surface temperature, its radiation per 
square inch of surf ace may be calculated; from the star's distance 
and apparent brightness, the radiation of the whole surface 



296 SCIENCE TEACHING 

may be estimated. Simple division gives the area of the surface. 
The later interferometer method gives results almost in exact 
agreement with the older method. 

By volume, 1,000,000 earths = i sun. 

10,000,000 suns = i Betelgeuse. 

But Betelgeuse has a mass of only about fifty times that of the 
sun; its vast bulk is due to the extreme diffuseness of its material. 
The matter constituting the universe has aggregated primarily 
into units of approximately equal masses. With few exceptions, 
they range from \ to 5 times the mass of the sun. The smallest 
known star is roughly the size of the earth. 

3. The Nebulce. The great spiral and other extra-galactic 
nebulae: consider these either as a family of stars, or of stars 
in the making, or as matter ultimately destined to form stars. 
Mass of each great nebula estimated to be equal to io y suns, but 
mass is so tenuous that each millionth part of an ounce has, on 
the average, a volume of several cubic miles. (The calculation is 
jo"" 16 gm. per cubic centimetre. The small amount of gas in 
an ordinary electric light bulb, if spread through a great hall 
like Olympia, would still be about 10,000 times as dense as 
the nucleus of a spiral nebula.) 

Estimated that about 2,000,000 great nebulae are visible in 
the great i co-inch telescope on Mt. Wilson. But only a com- 
paratively small fraction of the whole universe is visible in this 
telescope, viz. about io~ 9 . Hence the possible number of stars 
in the making is 

io 9 X 2.io 6 X io 9 == 2 X io 24 . 

4. Temperature and Energy of the Stars. We know from 
the nature of the light received from Betelgeuse that the surface 
temperature is 3000 C. But this gives us no idea of the great 
heat within. 

The greater the heat of a gas, the greater its expansive 
force. At any point inside a star, a certain condition of balance 
must be reached. On the one hand, we have the weight of all 



ASTRONOMY 297 

the layers above pressing down on the gas inside. On the other 
hand, we have the elasticity of this inside gas trying to expand 
and force the upper layers outward. Since neither the one 
thing nor the other happens, the two tendencies must just 
balance. At each point the elasticity, and therefore the heat, 
has to be of the exact amount needed to hear the weight of the 
layers above. That is the principal clue by which it is deter- 
mined how much heat there must be at various depths inside 
the star. The internal temperature depends on the particular 
star, but at the centre it is generally from 2 to 20 million 
degrees. This is not a temperature so vast that our ordinary 
ideas of temperature break down. Temperature is a mode of 
describing the speed of motion of the ultimate particles of 
the matter. In a mass of helium at ordinary temperatures, 
the average speed of the atom is rather less than a mile a second; 
at 4,000,000 it is 100 miles a second. 

A typical giant star must be conceived as a mass of material 
with an average density of about that of air, equal in volume to 
at least 1000 times the volume of the sun. The atoms of which 
it is composed are rushing in all directions, up to a speed of 
100 miles a second. The atomic energy constitutes a great 
store of heat contained in the star. But the star contains a 
further store of heat, aetherial heat or aether waves encaged 
by the material. In giant stars the heat is roughly equally 
divided between the two forms. 

A beam of light or aether waves exerts a pressure, just as 
a jet of water or a wind does (this is because it carries mass 
with it), a very minute pressure as a rule. But the intense 
aetherial energy inside a star makes a strong wind and exerts 
a great pressure. This wind-like pressure distends the star. 
To some extent it bears the weight of the layers above, leaving 
less for the elasticity of the inner gas to bear. The aetherial 
wind-pressure and the material elasticity together share the 
burden of supporting the weight of the layers above. The 
ratio in which they share it depends on the whole mass of the 
star, not on the density or on the chemical composition of the 
material. 



298 SCIENCE TEACHING 

Astronomers are able to estimate this ratio, and here is a 
summary of the results: " For globes up to io 32 grs., the material 
pressure is far greater than the aetherial. In globes of ID 33 , 
io 34 , and io 35 grs., the aetherial pressyre begins to be an impor- 
tant factor in the situation. In globes of io 36 grs. and above, 
the aetherial pressure is far greater than the material. The 
thousand million globes of gas in the skies are all of mass 
between io 33 and io 35 . The lightest known star comes just 
below io 33 , the heaviest just beyond io 35 ." 

" Were gravitation unresisted, it would build globes of 
enormous size. But setherial pressure is a disruptive force 
(doubtlessly helped by the ' centrifugal ' force of the star's 
rotation), and it prevents the accumulation of large masses. 
The aetherial pressure brings the accumulation to a halt as 
soon as io 35 grs. is reached, because by then it has become just 
powerful enough to master its opponent/' 

" As a gaseous star contracts, its temperature rises. Betel- 
geuse is typical of the first stage where the temperature has 
risen just far enough for the star to be luminous. It will go 
on contracting and becoming hotter, its light changing from 
red to yellow and then to white. When the condensation has 
proceeded far enough, the material will be too dense to follow 
the laws of a perfect gas. The rise of temperature then becomes 
less rapid, is checked, and finally falls. We can calculate that 
the greatest temperature is reached at a density of about -J to 
that of water. The sun is denser than water, so that it has 
passed the summit and is in the stage of falling temperature. 
As long as the temperature is rising, the brightness of the 
star scarcely changes; it is becoming hotter, but smaller. But 
on the downward path the light falls off rapidly, because of 
the falling temperature and diminishing surface. Through any 
given level of temperature, a star passes twice, once ascending, 
and once descending. The condensation of Betelgeuse will 
continue, and, perhaps after some billions of years, the star 
will become small and dense like the sun." 

" A star contains within itself energy to last the rest of its 
life. The greater part of the store of energy is energy of con- 



ASTRONOMY 299 

stitution of the atom and its electrons, i.e. sub-atomic energy. 
This store of energy inherent in the constitution of the electrons 
and protons cannot be set free unless the containing atoms are 
annihilated." 

" Probably the mattef of the star's hot central regions con- 
sists of a mixture of bare nuclei and free electrons. As we pass 
outwards towards the star's surface the temperature falls, and 
we come to atoms which are more or less fully formed, until 
finally, close to the surface, we meet with atoms fully formed." 

The spectroscope shows what elements are in the stellar 
surface. When the spectroscope is turned on Sirius, we see 
hydrogen and very little else. We do not on that account think 
that Sirius is made chiefly of hydrogen, but that its surface 
temperature is 10,000 C., because that is the temperature 
specially favourable for the hydrogen to show itself. 

There are three methods of estimating the ages of stars, 
and they lead to much the same results. The age is generally 
from 5 to 10 billion (5 x io 12 to 10 X io 12 ) years: this number 
is the general order of the magnitude of the age. 

5. Birth of Stars. Stars almost certainly had their origin 
in nebulae. Nebulae are huge masses of gas endowed with 
different amounts of rotation. Such a mass of gas not rotating 
would assume the shape of a sphere; rotating, it would become 
an oblate spheroid, and ultimately a disc-like structure. 
Examined spectroscopically, the nebulae are found to be rotating 
with high velocities about an axis which appears in the sky 
as the shortest diameter of the nebula. 

Mathematical theory shows that the cooling of such a 
rotatory flat oblate spheroid must cause it to condense and 
throw off detached portions. Nebular photographs actually 
show this in progress. Moreover the calculated estimates of 
the masses of the detached portions come out to just about 
the same as the masses of the stars. 

If a nebula is in rotation, its angular momentum must 
remain constant, and the shrunken mass can carry its original 
dose of angular momentum only by rotating more rapidly 

(K72) 21 



300 SCIENCE TEACHING 

than before, the effect of shrinkage being adjusted by change 
of shape. Further shrinkage leads to the breaking up of the 
nebula, matter being thrown off from the equatorial region. 

6. Birth of the Solar System -L? place's hypothesis fails; 
it does not stand mathematical investigation. If we work 
backwards from the present amount of spin in the system, 
calculation shows that the sun could never have had sufficient 
spin for bodies to separate from it. -At the moment Chamber- 
lin's hypothesis holds the field. Two stars may collide, though 
this must be very rare. Two may just escape colliding, huge 
tides are raised, and these may take the form of long streamers 
of gas. These streamers may issue with such velocity that 
they may break away, just as if huge bolts were shot forth from 
the sun. Quite probably the planets were formed in this way. 
But such close approach must be rare. Calculation shows that, 
even after billions of years, only about one star in 100,000 
can be surrounded by planets born in this way. In the io 9 
stars in the visible universe, there are probably not more than 
10,000 planetary systems. There is perhaps one birth every 
io 9 years. Contrast the birth of the solar system with the birth 
of the stars. 

7. The Sun.- The sun radiates enough energy from each 
square inch of its surface to keep a 5O-h.p. engine continually 
in action. Still hotter stars may radiate as much as 30,000 h.p. 
per square inch. A searchlight which is radiating 50 h.p. of 
energy is discharging with the radiation into space mass at 
the rate of i-J grams a century. The sun's surface is so large 
that the sun as a whole is discharging mass at the rate of 
250,000,000 tons a minute. Now the sun has no source of 
replenishment. It must have weighed 360,000,000,000 tons 
more yesterday than to-day. We can calculate that 5 or io 
billion years ago, the sun must have been several times as 
massive as it is to-day. Thus young stars are probably many 
times as massive as old stars. The radiation which has been 
produced continuously for billions of years must, presumably, 
have been due to the annihilation of electrons and protons. 



ASTRONOMY 301 

The surface temperature of the sun is about 6000 C. 
When the sun was in its prime, that temperature was probably 
6600 C.; it has not mass enough for the temperature to be 
much higher. 

The age of the sun is perhaps io 10 years, perhaps half as 
much again. The mass of the sun is 2 X io 27 tons. 

A billion (io 12 ) years hence, the sun will probably be much 
as now, with the earth revolving round it much as now. The 
year will be a little longer, and the climate considerably colder. 

8. Eclipse Prediction. The discoveries of the ancient 
astronomers. The Saros and its factors. Modern accuracy of 
prediction, and why more so than in ancient times. 

9. Newton. The full story of his discovery of the law of 
gravitation. 

10. Short History of Astronomy. The pioneers. Present- 
day workers. 

11. The Calendar. A fixed Easter? Advantages. Objec- 
tions mostly of a sentimental kind. The more general reform 
of the calendar; the present illogical calendar division indefen- 
sible. Daylight saving. 

Throughout these lectures, the teacher should emphasize 
the fact that most of our knowledge of the stellar system is 
merely inferential, even speculative. The interpretation of the 
available spectroscopic data is largely hypothetical, though our 
leading astronomers do, it is true, agree about main conclusions. 
It seems probable that the main hypotheses are in harmony 
with the facts, but we cannot say more than this. 



Books 

Do not despise some of the older works. The names of Herschel, 
Ball, Lockyer, Proctor, and others are proverbial for their lucid 



302 SCIENCE TEACHING 

explanation of difficulties in connexion with the solar system, ^ct 
every boy read Sir R. Gregory's The Vault of Heaven; it is a most 
teacher-like book. This might be followed by Astronomy with the 
naked eye. For Astrophysics, consult H. Dingle's Modern Astro- 
physics. For recent work, see Professor pddington's Internal Con- 
stitution of the Stars , and Sir James Jeans J s books. 



CHAPTER XXVII 

Science in Rural Schools 

The Kind of Work that is Advisable 

Farmers have little confidence in school courses of agri- 
culture, contending, possibly justly, that science teachers can- 
not have an inner knowledge of agricultural practice. And in 
order that boys may be induced to take an interest in rural 
life, it is no longer considered necessary to make agriculture 
a subject of school instruction. Scientific agriculture is now 
systematically taught at the agricultural colleges and farm insti- 
tutes where there are naturally much great facilities than can 
be provided in schools. 

But a course of instruction with a definitely rural bias is a 
different thing. The term " rural bias " connotes such modi- 
fications of the commonly accepted scheme of work in science, 
mathematics, and manual instruction as are necessary to make 
these subjects suitable for rural schools. Although such modified 
science courses, like all school science courses, must be laid upon 
foundations of physics and chemistry, it is the study of plant and 
animal life, and the relation of these to the soil and to the atmos- 
phere, that are the main things to be kept in view. Experiments 
in the garden as well as in the laboratory must receive special 
attention. Such a course should not be a feeble copy of a course 
at an agricultural college; primarily it will be educational and 
not technical. Technical matters of purely professional interest 
to the future farmer will be omitted. The breeding and manage- 



SCIENCE IN RURAL SCHOOLS 303 

ment of stock and the diseases of stock, for instance, are subjects 
unsuitable for school work; so are such crafts as farriery and 
hedging; so are butter-making and cheese-making. 

The subject of agriculture is so large and touches upon so 
many branches of knowledge that, even at an agricultural college, 
selection becomes imperative; otherwise, there will be too 
little training in observation and experiment, and too much 
compiling of encyclopaedic note-books on farming. In drafting 
a school science course with a rural bias, a teacher must be 
ruthless in cutting out all topics which either do not lend them- 
selves readily to observational and experimental work or are 
unrelated to general principles. 

The course must provide a training as exacting as courses 
of the more severely academic kind. The training must be 
such as to equip a boy, who is to enter upon an agricultural 
course at the university or agricultural college, in such a way 
as to make it unnecessary for him to spend much time there 
in learning " pure " science: it is assumed that such boys will 
spend at least one year in the Sixth Form. But the training 
must also provide adequately for the boy who at 1 6 or 17 
goes back to his father's farm, by which time he should be able 
to grasp the content of a book on agricultural chemistry and 
kindred subjects and so continue a self-education on technical 
lines. And both classes of boys should be encouraged to aim 
at fitting up, on the farm they some day hope to run, a well- 
equipped chemical and biological laboratory. 

Drawing Up a Course: Some Principles 

A clear understanding of the processes of plant and animal 
life, and of soil cultivation, depends upon a knowledge of the 
fundamentals of physics, chemistry, and biology. The first 
thing to do is to map out a course in these three subjects, 
bearing in mind all along, when establishing principles, the 
possible applications and illustrations that may be drawn from 
rural life, though the bare bones of the three subjects will be 
almost identical with those in any other science course. For 



304 SCIENCE TEACHING 

instance: phosphorus and phosphoric acid will be included in 
the chemistry course because they are required for the study 
of phosphatic manures; carbohydrates and fats will be included 
in the chemistry course because they aye necessary for explain- 
ing feeding values; osmosis will be included in the physics 
course in order to illustrate (amongst many other things), the 
danger of applying large dressings of nitrate of soda; the general 
characters of gramineous plants will be included in the botany 
course, in order that the lessons learnt may be afterwards 
applied to the special characters of wheat, oats, barley, &c. 
And so generally. Jot down the hundred and one things the 
future farmer ought to know; sort out the underlying principles 
of physics, chemistry, and biology, and classify them; then fill 
in gaps in order to frame rationally developed courses in the 
three science subjects. These courses should be so designed 
as both to afford a rigorous training in scientific method and 
to provide the scientific facts and principles wherewith to 
explain and illustrate processes in farming operations. It is 
these processes that give a bias to the course. Some more 
complex process may touch upon more than one of the three 
main subjects; for instance, the principle of the rotation of 
crops has relation to (i) the distribution of root-systems; (ii) 
the selective power of the plant in regard to substances in 
solution; (iii) the nitrogen cycle. Clearly the appropriate 
selection of topics is of fundamental importance for teaching 
purposes. 

Suggested Outline Courses 

PHYSICS. Densities. Fluid pressure. Osmosis (elementary 
treatment, but thorough). Soil physics (highly important). 
Surface tension (elementary) and capillarity. Elementary heat. 
The steam-engine and the internal-combustion engine. The 
visible and invisible spectrum. The electric current and electric 
supply (of coming importance in rural districts). 

MECHANICS. Elementary principles, illustrated by machines 
(only elementary mathematical treatment necessary). Levers, 
pulley-blocks, screw-jacks, trains of wheels, belts and shafting. 



SCIENCE IN RURAL SCHOOLS 305 

simple roof-structures, and so on, bearing in mind farm out- 
buildings, and the mechanical devices employed in farm imple- 
ments. The mechanism of the steam-engine and the internal- 
combustion engine. | 

CHEMISTRY. Qualitative and quantitative study of air and 
water. Combustion; oxides; acids, bases, salts. S, H 2 SO 4 , 
the sulphates. Cl, NaCl, HC1, the chlorides. N, NH 3 , HNO 3 , 
the nitrates; putrefaction and nitrification. P, H 3 PO 4 , the 
phosphates. Silica, sand, clay. Carbon and its oxides. Car- 
bonates and hardness of water. (See Dymond's book.) 

Compounds that are of interest to only the professional 
chemist should not be included. Something of the nature 
of such bodies as alcohol, fat, glycerine, soap, sugar, starch, 
and carbolic acid should be known, and therefore a brief 
course of organic work is desirable. Include also such chemical 
facts and processes as may have any sort of bearing on agri- 
cultural practice or are of agricultural significance. The 
chemistry course should be carried far enough to enable the 
pupils to understand the laws of chemical combination and the 
meaning of a chemical equation. The chemical analysis of the 
soil must be reserved for Form VI, though the estimation of 
the amount of water, soluble matter, and humus in the soil 
may be undertaken by pupils in IV and V. The practical 
work may well lean a little in the direction of analysis, quali- 
tative and quantitative (gravimetric and volumetric in VI). 
The preparation of a few typical salts should be included in 
the course, and the younger pupils might be given a special 
course on solubility and crystallization. 

BIOLOGY. (i) Botany. Morphology and classification should 
receive some attention, but function should stand first: trans- 
piration, respiration, root-pressure and osmosis, photosynthesis. 
Culture solutions. The life of flowering plants, including 
grasses, and the function of their vegetation and reproductive 
organs, based on a study of familiar types. Germination (may 
be hastened in winter by keeping an incandescent lamp about 
2 inches above the seeds, the seeds being just covered with 
wet saw-dust). Vegetative reproduction cuttings, layers, 



306 SCIENCE TEACHING 

budding, grafting. Pollination. The study of a few orders of 
economic importance: Gramince true grasses and cereals; 
common grasses on the farm; Cruciferce cabbage, turnips, 
swedes; Rosace fe plums, cherries, apnles, pears; Leguminosa 
beans, peas, vetches; Umbelliferce carrots, parsnips. Weeds 
on the farm; injurious effects; habits; extermination. 

(ii) Zoology. Some common small animal (say rabbit) 
should be dissected, its organs identified, and its general 
physiology understood. There should also be a practical 
study of the metamorphosis of the frog and a few common 
insects (say, bee, beetle, moth, daddy-long-legs, dragon-fly, 
water-boatman). Outlines of the classification of animals. 
Observations of local wild animals, birds, and insects; their 
haunts and ways. Farmers' pests and preventive measures. 

Out-of-door Practical Work 

Plot for Seed Experiments. Sow seed (i) at different 
depths; (2) at different dates; (3) of different sizes; (4) thickly 
and thinly; (5) in fine and in coarse tilth; (6) in varying degrees 
of dryness. Thinning at various stages of growth. Of course 
the seed must be sown by hand, and to that extent is not prac- 
tical farming. 

Cultivation. Shallow and deep digging; trenching; influ- 
ence of these in first and successive seasons. Raking and 
compressing the soil surface; harrowing and rolling. Influence 
of different kinds of manures on plant growth. 

Five Small Plots. To show the effect of no manure, no 
nitrogen, no phosphate, no potash, a complete manure (on 
such typical crops as barley, clover, cabbage, beet, mangels, 
grass). 

Comparative Studies. Sow the winter bean, the Windsor 
bean, the garden pea, the sweet pea, the everlasting pea, the 
scarlet runner, the French bean, and the garden lupin. Note 
differences in morphology of root, stem, leaf, flower; in methods 
of climbing, methods of pollination, the turning down of polli- 
nated flowers, methods of seed dispersal. 



SCIENCE IN RURAL SCHOOLS 307 

Order Plots. For gramineae, cruciferae, rosaceae, legumin- 
osae, umbelliferae. 

Fruit Plots and Rose Plots. These should be large enough 
for permanent bush-trera of apples and pears, gooseberry 
bushes, red and black currant bushes, and a variety of bush 
roses. Propagation work seedlings, cuttings, layering, bud- 
ding, grafting. Plant fruit tree and rose stocks; raise paradise 
cuttings for apple stocks; and brier cuttings for rose stocks. 
Pruning: the development of dormant buds; influencing the 
shape of a tree. Insecticide and fungicide washes. 

All this outside work should be essentially of an experi- 
mental character, supplementing the work of the laboratory. 
It should not be looked on as mere gardening. The work should 
not only encourage an open mind, but encourage a reluctance 
to follow blindly an established practice. 



Other Supplementary and Complementary Work 

Border-line subjects, associated with mathematics, me- 
chanics, mechanical drawing, and manual instruction: 

1. Plans, elevations, and construction of farm buildings. 

2. Construction of different kinds of fences. 

3. Farm machinery and implements, and their construction. 

4. Farm drainage and water supply. 

5. Chain surveying; levelling (at least as far as is necessitated by 
a drainage system). 

6. The cubical content of stacks. 

7. Manual work: construction (in the school workshops) of a 
garden gate, a five-bar gate, wheelbarrow, roof-truss, drinking- trough, 
stile, ladder, &c.; hinges, stays, staples, latches, linch-pins, &c. 
Simple plumbing, e.g. the making of lead gutters. Use of galvanized 
iron. Repairs to broken implements. Different kinds of timber. 
Common building materials, nature and uses. 

Every farmer ought to be able to judge intelligently, if not 
actually to make, the implements and structures pertaining 
to the farm. 



308 SCIENCE TEACHING 

Sixth Form Work 

All branches of the subject may be carried by a Sixth Form 
to a higher standard. In particular, much more advanced 
chemistry may be done. It might include the special study of 
the important bases and acids of common occurrence in soils 
and manures, and the organic compounds in feeding-stuffs. 

The abler boys might try agricultural experiments, say on 
crop production. Some remarkable experiments on wheat 
production were carried out at Oundle in 1910-1. Teachers 
interested in this kind of work might make inquiries about 
present-day work there. The Head Master of Dauntsey 
Agricultural School should also be consulted. And there is 
always Rothamsted willing, even anxious, to advise. 

Books for Reference 

See the Science Masters' Association Library Catalogue. The 
Board of Education have issued special Reports on Rural School work, 
and these should be consulted. Mr. Dymond's Chemistry for Agricul- 
tural Students and Percival's Agricultural Botany should be read by 
all Rural School Science teachers. 



CHAPTER XXVIII 

Domestic Science 

"Science" or "Craft"? 

" Domestic science " is a term sometimes given to house- 
craft as an art, sometimes to a sort of pseudo-science supposed 
to supplement the craft work, especially on the food side. 
The work done has rarely much claim to rank as " science ", 
in the correct sense of the term. 

A domestic science course sometimes begins in much the 
same way as courses in elementary physics and chemistry, 
and then suddenly and much too soon launches off into what 



DOMESTIC SCIENCE 309 

purports to be organic and physiological chemistry, without 
establishing any real connexion with the work already done. 
The books used are too often mere small encyclopaedias of 
useful knowledge. The true aim of science teaching is missed. 
No definite body of general doctrine is built up. Principles 
may be laid down, but they are too often laid down on a basis 
of insufficient evidence. The work is too superficial, and the 
preliminary grounding is altogether insufficient. It is not 
realized, for instance, that even the simple study of carbo- 
hydrates and fats presupposes a preliminary training in 
elementary organic chemistry, much more than is usually 
attempted; and that the study of proteins demands a ground- 
ing in organic chemistry that is seldom possible in girls' schools. 

The question is sometimes asked, Is it of any use even 
to attempt to give school housecraft a scientific basis? Is a 
woman likely to make a better cook because she knows the 
chemical reactions of baking-powder? or is she likely to select 
and cook a joint better because she knows that the protein in 
the meat is myosin? It will not be denied that if a better 
practical cook is the desired end, one lesson in the kitchen 
is worth two in the laboratory. Moreover, a laboratory course 
which consists of just a succession of useful little experiments, 
scarcely related and not associated, may teach useful facts, 
but it cannot provide that particular form of exacting training 
which is the special function of a science course. 

Admittedly every intelligent woman who runs a house 
ought to know the rationale of most of the processes and hap- 
penings in her daily environment. For instance, in mechanics 
and mechanism, the reading of meters, the regulation of clocks, 
the uses of lubricants, the mechanism of the knife-machine, 
the vacuum cleaner, the sewing-machine, and the bicycle-pump, 
taps and cisterns, drains and traps, the capacity of different 
vessels (tea-spoon, table-spoon, wine-glass, &c.); in heat and 
heating, thermometers, fixed stoppers, kitchen-ranges, hot- 
water systems, the thermos flask, burst pipes, freezing-mixtures 
and ice creams, damp clothing, fabrics, the bronchitis kettle, 
steam scalds, the relative heat values of coal, coke, gas, oil, 



3 io SCIENCE TEACHING 

and electricity, ventilation; in lighting, oil, gas, and elec.ric 
lighting, management of burners, mantles, lamps, switcies, 
fuses. 

With such topics as these before her, the responsible mis- 
tress may formulate a syllabus of instruction in physics, v ling 
in gaps to give the course a rational sequence. The main ject 
would be to give a clear understanding of principles. The 
house problems would then no longer be rule-of-thumb affairs 
but applications of known principles of science. 

In the strictly educational sense, however, science often 
plays but a humble part in this kind of work. Let us consider 
a particular phenomenon, say that of a " burst " kitchen boiler. 
The ordinary housewife will not improbably have been told 
during her domestic science course that cold water admitted to 
a dry red-hot boiler causes the boiler to " burst ". True she 
has learnt a useful fact, namely, that cold water must not be 
admitted to a dry red-hot boiler. But when she states that 
the boiler will " burst ", she states a common fallacy, and 
shows that her training in elementary science has not been 
serious. With clear notions of latent heat and calorimetry, 
she would know that the result would be only a fracture, and 
not even that if the plates were of steel. This does not mean 
that she should necessarily have worked numerous quantitative 
experiments in calorimetry, but she should have done enough to 
know that the amount of heat stored away in the red-hot plates 
is altogether insufficient to convert more than a very small 
quantity of the inflowing cold water into steam, and that the 
resulting steam pressure will be relatively negligible. She 
ought to have learnt that the danger of a burst can arise only 
when the return or vent pipe is blocked up, that then the 
pressure in the system brings about a high temperature, and 
a fracture leads to an immediate conversion of the whole of 
the water into steam. The properly trained pupil will have 
learnt all this from her earlier course on heat. The cook-book- 
recipe-supplied housewife will think in terms of a big bang, 
a nasty mess, and possible personal danger; she will certainly 
not think scientifically. 



DOMESTIC SCIENCE 311 



Cleaning Agents and Operations 

There are, however, parts of the usual housecraft course 
that lend themselves to <i fairly satisfactory treatment. The 
subject of cleaning operations is one. Although this subject 
is so varied that it cannot be cast into the form of an entirely 
satisfactory scheme of science instruction, its parts may yet 
be classified and dealt with in a reasonably intelligent manner. 
General principles : e.g. : 

1. The close relationship between dirt and disease. 

2. A cleaning operation may consist of two distinct processes; 
for instance: 

(a) The breaking up of a greasy deposit; 

(b) The removal by mechanical means of the dust now set free. 

3. Choice of a suitable solvent, e.g. one that will dissolve or unite 
with grease without injuring the material. 

4. Choice of a suitable cleansing agent in order that the " finish " 
of the article operated on may not be impaired. 

5. Distinction between surface dirt (e.g. on wood or wallpaper) 
and dirt settled amongst the fibres of fabrics. 

6. The necessity for preserving the colour as well as the texture 
of materials. 

7. The limitations of cleansing agents. 

Preliminary classification of things to be cleaned. 

1. Fabrics, furs, feathers, gloves, hats, &c. 

2. Paper, parchment, vellum, prints, pictures. 

3. Linoleum, oil-cloth, carpets, rugs, skins; leather. 

4. Wood-furniture painted, stained, polished, &c. 

5. Marble, stone, plaster, alabaster, porcelain, glass (mirrors, 
windows, decanters, &c.). 

6. Metals: brass, copper, burnished steel, soft metals (tin, zinc, 
&c.), silver-ware; stoves, metal bath-tubs, metal lamps, &c. 

7. " Paint ", e.g. doors, window-frames, &c. 

8. Various, e.g. sponge; ivory, bone, and composition articles. 

Preliminary classification of stains t tarnishes y &c. 

1. Dust free, and fixed by films of grease, &c. The nature and 
origin of dust. 

2. Soot and smoky deposits. 



312 SCIENCE TEACHING 

3. Grease, oil and wax; stains and deposits. 

4. Fruit stains on metals and fabrics, food stains, tea and coffee 
stains, wine stains. 

5. Medicine stains; blood stains. 

6. Ink stains: black ink, red ink, aniline ink, printer's ink. Iron 
stains and rust spots. 

7. Acid stains: stains from alkalis. 

8. Pitch, tar, paint: on clothing and on the hands. 

9. The white mark on a polished table, e.g. from a hot dish. 

10. The tarnish on metals. Oxides: how they are alike and how 
they differ. 

11. Mildew: how it differs from a stain. 

Cleansing agents: their nature. Classification and comparative study. 

1. Fresh air and sunlight: their action. The use of a damp cloth. 
" Shaking." 

2. Water: cold, warm, and boiling. Comparative study of these 
as cleansing agents. Effects of boiling water on fabrics, e.g. woollen 
goods and prints; any injurious effects? 

3. Action of dry heat: e.g. the use of a hot iron held over a spot 
of grease or wax? 

4. Soaps: comparison of their detergent properties. 

5. Alkaline solutions: AmHO, NaHO, KHO; comparative study. 
Cold and hot solutions of washing-soda. Soap-powders. Saponifi- 
cation; emulsions. 

6. Comparative study of citric acid (including the cut surface 
of lemons), tartaric acid (cold and hot solutions), oxalic acid, acetic 
acid, hydrochloric acid. 

7. Naphtha, turpentine, alcohol, ether, benzine, petrol; compara- 
tive study of their solvent properties; the dangerous nature of the 
last three: warnings. 

8. Ashes, emery, powdered pumice, rottenstone (and oil), powdered 
chalk, whiting. 

9. Bran (and hot bran, for feathers), meal, saw-dust, starch (in- 
cluding paste of cold-water starch). French chalk. Fuller's earth, 
The special work of absorbents. 

10. Bleaching powder, sulphur dioxide, and perhaps hydrogen 
dioxide. 

11. Brass polish, globe polish, " monkey soap ", furniture polish, 
plate powder, &c. Composition of polishes; hence their probable 
action. 

12. Various agents: e.g. bread crumbs; skim milk, buttermilk; 
ox-gall; borax, boracic acid; glycerine; " florigene ", &c. 



DOMESTIC SCIENCE 313 

Systematic study of cleaning, reduced as far as possible to simple 
experimental problems of investigation. For instance: 

1. The need of softening pitch or tar with grease or oil before 
applying turpentine or alcohol. 

2. The difficulty of removing ink stains because of the uncertainty 
of the composition of the inK. Successive applications of cold water, 
tepid water, skim milk, oxalic acid. The advantage of attacking an 
ink stain at once say by sprinkling with salt and rubbing with lemon 
pulp. Action here? 

3. The nature of mildew. Simple remedies for removal; the 
probable effect of the more drastic remedies. 

4. If acid dropped on clothing, why immediately apply an alkali? 
When acids are used for cleansing purposes, why follow up with 
alkalis and then hot water? If strong alkalis used, why follow up with 
acids? Are strong acids desirable? 

5. Marking-ink stains. The composition of the ink; hence method 
of attack. 

6. The nature of bleaching, and the study of chloride of lime. 
The possible destruction of the fibres and of the colours. Can this 
be avoided? Sulphur dioxide as an alternative; when it should be 
used. 

7. Comparative study of turpentine, benzine, ether, and petrol 
for taking grease out of coarse and out of delicate fabrics. The danger 
of using these agents; warn again. 

8. The study of alcohol as a solvent. Hence the action of brandy, 
whisky, perfume, &c., if spilled on a polished table. Remedy? 

9. The use of vaseline for preventing polished metals from rusting. 

10. Vacuum cleaning; action? *' Dry " cleaning; action? 

The work of the laundry. Revision of work already done. 

1 . Hard and soft w r ater; how to soften water. 

2. Soaps and soap substitutes. Washing-soda, ammonia, borax, 
and other materials used in the laundry. Their action and use. 

3. The general study of alkalis as used in the laundry. 

4. Bleaching and bleaching agents. The use of blue. 

5. Stiffening agents. 

6. The various processes of the laundry classified and analysed 
according to the scientific principles underlying them. 

The household laboratory. 

i. Supplies of benzine, turpentine, ox-gall, tartaric acid, oxalic 
acid, hydrochloric acid, chloride of lime, ammonia, caustic soda, 
French chalk, Fuller's earth. Their practical use. 



314 SCIENCE TEACHING 

2. Supplies of potassium permanganate, boric acid, boric wool 
and lint, carbolic acid, formaline, and a very small quantity of 
corrosive sublimate. The preparation of instructions for their use in 
emergency. 

Useful as such a course may he/made, it certainly has its 
limitations from the point of view of training in science. The 
course does not lend itself to the building up of a consistently 
logical body of doctrine. It is an intelligent treatment of a 
group of associated facts rather than the teaching of science. 

Now consider the much more difficult subject of foods and 
food-substances. We will select the most difficult of all, the 
group commonly called " proteins ". It may be assumed that 
the pupil has already done a course of elementary inorganic 
chemistry, and has already done something to the easier parts 
of the study of food substances, say carbohydrates, fats and 
oils, milk, and flour. It is not assumed that she has done 
any appreciable amount of organic chemistry. 

The Study of Proteins * 

1. Examine a fresh egg. An egg is really an undeveloped chick. 
Since the chick is developed from the egg, the egg must contain 
within itself all the building material necessary for the making of the 
chick, together with such a supply of nutriment as the latter requires 
until it is ready to be hatched. Weight of egg about 50 gm. (2 oz.): 
shell 12 per cent; white ~ 58 per cent; yolk = 30 per cent. 

2. Composition of shell! The white is a solution of protein shut 
up within a multitude of cells. " Beating up " the white of egg rup- 
tures the cell-walls; the protein thus escapes, and the digestibility of 
the egg-white is increased. This protein is called egg-albumin. The 
yolk is the storehouse of nutriment for the young chick: contains a 
large proportion of fat palmitin, stearin, and olein present in the 
form of emulsion, and therefore easily digested. How could the 
presence of fat be proved? Colour of shell makes no difference to 
the composition of the egg. When kept, eggs become lighter; why? 
Cause of disagreeable smell in bad eggs. How to tell a fresh egg. 
Relative digestibility of raw eggs, lightly boiled eggs, and hard boiled 
eggs. Nutritive value of eggs. Custard powders. 

* The old distinction between " proteid " and " protein " no longer obtains, 
and the latter term is in general use. 



DOMESTIC SCIENCE 315 

3. Examine egg-albumin (egg-white). Reaction with litmus? 
Solubility? 

4. The action of heat upon egg- albumin. (Heat in test-tube in 
beaker of water.) Becomes cloudy at 58 C.; coagulates at 60. Is 
coagulated albumin solublel Heat more albumin in crucible to higher 
temperature; odour? Cf. wnh the heating of gluten. Put a little egg- 
albumin aside for a few days; putrefaction: nature of gas given off. 

5. Dry some egg-albumin over a water-bath, mix it with soda- 
lime, and heat strongly in a test-tube. Ammonia now easily detected. 
Hence the albumin is a compound of nitrogen. The casein of milk- 
curd, the gluten of flour, the albumin of the egg, are all nitrogen com- 
pounds and belong to the class of food-stuffs known as proteins. 

6. Examine some raw lean beef or mutton. Note bundles of 
fibres. How are the fibres held together? 

7. Dry some lean meat in an air-oven (temperature ioo-iO5). 
Percentage of contained water. Reduce the dried product by further 
heating to a white ash: percentage of mineral matter in lean meat. 
Composition of lean meat: 50 to 75 per cent of water, about 20 per 
cent of protein, with fat and mineral matter. The chief protein 
present is myosin. Composition of fish much the same: but some fish 
are very free from fat, while others are remarkable for the amount of 
oil they contain. 

8. Effect of boiling on meat. Place in cold water, heat gradually, 
and note temperatures of changes. Water becomes cloudy at 58; 
why? At about 71, a scum forms; cause? Let the water simmer for 
half an hour, and record all changes; take out the meat and examine. 
Now plunge a piece of raw meat into boiling water. Contrast with 
previous experiment. Take out as before and examine. Cause of the 
formation of the " crust ". Its use. How are the contained juices 
prevented from escaping? Cf. the boiling of fish. Any objection to 
putting fish into boiling water? Roasting; broiling; frying: compare 
and contrast these methods with boiling. Cf. methods of cooking 
different joints. Stewing. Steaming. Reasons for cooking meat. 

9. Beef-juices; beef- tea; bovril. Meat-extractives generally. 
Liebig's extract almost devoid of protein; mainly an exciter of gastric 
secretion; not a food, and even a doubtful stimulant. 

10. Peas, beans, and lentils, all rich in nitrogen. Why, then, 
described as the " poor man's beef "? The contained protein is 
legumin. Legumin unites with lime salts, forming an insoluble com- 
pound. Why, then, is it difficult to cook peas and beans in hard 
water? Use of soda in the cooking. Nutritive value and digestibility 
of peas, beans, and lentils. 

This is all very useful knowledge, the treatment is logical, 

(K72) 22 



316 SCIENCE TEACHING 

the experiments are mostly simple, and the facts stated without 
resort to experiment are, in the circumstances, permissible. 
But is such teaching science teaching? It is characterized by 
a repetition of very elementary experiments of much the same 
order of difficulty. No matter how excellent the actual teaching 
may be, it cannot be said that the work done is very exacting, 
or that the reasoning is very rigorous, or that there is a very 
serious training in systematized procedure. In short, it can 
hardly be regarded as work worthy of intelligent Sixth Form 
girls. The fact that the girls have no knowledge of organic 
chemistry makes it impossible to treat the subject as it ought 
to be treated from the point of view of science. 

It is probably best to include all this kind of work under 
the head of housecraft. The principles of physics and chemistry 
are best taught independently, mainly before housecraft as a 
separate subject is taken up. Then the housecraft may be 
placed on a fairly rational, if not on a strictly scientific, basis. 
Reasons for processes will be discovered and understood, and 
homecraft may then become something more than a traditional 
routine, followed because mother followed it and she because 
her mother followed it, and so on. The subject as taught will 
consist largely of applications of principles of physics and 
chemistry already known, and in this way the earlier course 
in science, being used to throw light on new knowledge, will 
be greatly increased in value. But it is wiser not to talk about 
domestic science. It is preferable for the science mistress and 
the housecraft mistress each to stick to her own last. The 
two will collaborate closely, and although one will be teaching 
science and the other a craft, each will make constant use of 
the work of the other. 



METEOROLOGY AND WEATHER FORECASTING 317 
CHAPTER XXIX 

Meteorology and Weather Forecasting 

The Newer Aspects of the Subject 

Since the beginning of the present century, our knowledge 
of the atmosphere has increased enormously, knowledge which 
has revolutionized our ideas of meteorology. Instead of ranking 
as a body of rather crude empiricism and doubtful conjecture, 
as it did thirty years ago, meteorology is now fairly definitely 
established on a scientific basis. The forecaster's work has 
become comparatively easy and certain. 

If the subject is taught at all and about this there is 
great difference of opinion the following points seem to 
demand preliminary exposition and explanation: 

STRUCTURE OF THE ATMOSPHERE. From the point of view 
of temperature, there are two shells or regions: a lower shell 
or region in which there is a fairly rapid " lapse " of tempera- 
ture upwards, and an upper shell or region in which the lapse 
rate is approximately zero. An ascent shows that the transition 
from the region of falling temperature to the region where 
there is virtually no change with further height, is generally 
abrupt. The level at which this change takes place varies from 
5 to 8 miles up. 

But the upper region is not a region of uniform tempera- 
ture. In the lower region, the isothermal surfaces are parallel 
to the surface of the earth. In the upper region, the isothermal 
surfaces are not even approximately horizontal; they are practi- 
cally vertical. 

The upper shell, in which there is no material change of 
temperature with height, is called the stratosphere. The lower 
shell, in which, as we have long known, the temperature lapses 
with the height, is called the troposphere. 

We may look upon the stratosphere as the normal part of 
the whole atmosphere, the part unmodified by earth-surface 
conditions. It may be visualized as vertical columns or sheets, 



318 SCIENCE TEACHING 

each of practically uniform temperature: the isothermal sur- 
faces are vertical. The troposphere consists of those lower parts 
of the atmosphere which, with the aid of water-vapour, have 
been modified by convection. It maj be visualized as approxi- 
mately horizontal layers, each of practically uniform tempera- 
ture: the isothermal surfaces are horizontal. 

The troposphere is not of uniform thickness; it is about 
twice the thickness at the equator as it is at the poles. Its upper 
boundary is called the tropopause and marks the limit of the 
operation of convection. If there was no convection the 
atmosphere would be all stratosphere. 

Evidently the tropopause is not horizontal, though the 
stratosphere rests on it like a layer of oil on a layer of water. 
The tropopause is not fixed but is constantly fluctuating. 

There is an unexpected and noteworthy reversal that all 
students of meteorology must bear in mind. In the tropo- 
sphere, the temperature not only decreases with height, but, 
at corresponding heights, it also decreases as we pass from 
the equator to the poles. In the stratosphere, the temperature 
does not decrease with height, and vertically it remains practi- 
cally unchanged, though, at corresponding heights, it increases 
as we pass from the equator to the poles. For instance, at the 
earth's surface, the mean annual temperature at the equator is 
50 warmer than at the poles; but at 12 miles above the surface, 
that is, in the stratosphere, the temperature difference at the 
equator and poles happens to be the same as before (50), 
but in this case it is the polar region which is the warmer a 
truly amazing reversal! 

The tropopause may be visualized as a permanently separat- 
ing surface between the stratosphere above with its vertical 
isothermal surfaces, and the troposphere below with its hori- 
zontal isothermal surfaces; now rising a little, locally, now 
falling a little, locally, depending on the convectional activity 
of the troposphere. 

SOURCE OF ENERGY/ For the meteorologist, water in the 
form of vapour is the most important constituent of the 



METEOROLOGY AND WEATHER FORECASTING 319 

atmosphere. It provides not only the material for clouds, 
rain, snow, and hail, but also the means of supplying the energy 
which makes these things possible. Important meteorological 
functions hitherto attributed to warm air are now known to 
belong to the vapour which the warm air carries. 

We may look upon the troposphere as originating in the 
persistent digging away of the underside of the stratosphere 
by convection of one sort or another which itself originates in 
the warmth and moisture developed at the earth's surface or 
in the loss of heat in the absence of the sun. Convection is 
largely dependent on water vapour. 

The troposphere may be looked upon as the flywheel of 
a gigantic heat-engine an engine for converting solar energy 
into the energy of the winds. It is in a state of perpetual 
motion, which we call the circulation of the atmosphere the 
dynamical effect of heat received from the sun by radiation, 
communicated chiefly at the ground-level, and afterwards 
radiated into space. 

It is known that the diminution of the intensity of solar 
radiation with the increasing obliquity of the sun's rays is due 
to absorption by the atmosphere, principally by the contained 
water vapour. If there was no water in the atmosphere, the 
intensity of solar radiation would reach and remain at a maxi- 
mum throughout the period of sunlight, changing instantan- 
eously to zero with the disappearance of the sun at sunset. 

The main problem is: how does the atmospheric engine work? 

MOVEMENTS OF THE AIR. The decrease in temperature of 
the troposphere as we ascend varies from place to place and 
from time to time, but the average decrease is practically the 
same in all parts of the world. If we ignore the complicated 
conditions near the ground, the " lapse-rate " is the same for 
all parts of the world, from the equator to the poles; it increases 
regularly as we ascend. Whether air will rise or fall as the 
result of differences of temperature depends not only on an 
initial difference of temperature but also on the lapse-rate in 
the surrounding atmosphere. After rising a little way, a mass 



320 SCIENCE TEACHING 

of air may have no buoyancy left. But the question of ascend- 
ing and descending air is complicated by the condensation of 
the water- vapour carried with it, and we can best take this 
into account by considerations of enti|3py. 

Sir Napier Shaw has preparea diagrams showing the 
entropy throughout the normal atmosphere. These show 
surfaces of constant entropy that are nearly horizontal, lying 
almost like a series of stratified rocks. 

On all movements of air in which heat is neither added 
nor extracted for instance, by condensation or radiation it 
must travel along an isentropic * surface. These isentropic 
surfaces act like physical restraints to the air, tending to pre- 
vent its moving in any but an almost horizontal direction. 
This thermal stratification rules out ascending and descending 
currents as a direct consequence of the normal temperature 
distribution of the atmosphere. That ascending currents do 
occur is, of course, true; we infer them, for instance, from the 
large amount of precipitation we measure. But in the stratified 
atjnosphere these ascending currents are possible only if the 
air taking part in them receives sufficient heat on its ascent to 
raise its entropy at least to that of the surrounding atmosphere 
at each level. Heat is supplied by condensation of water- 
vapour, but normally air does not hold sufficient water-vapour 
to supply the requisite heat, and so cannot pierce the normal 
stratification. 

The descent of air is a different matter, but air cannot 
descend through the stratification without the necessary heat 
being extracted. On the other hand, we know that air does 
descend, for an amount of air equivalent to that which goes 
up in ascending currents must come down somewhere. The 
solution of the problem seems to be that, practically, air never 
descends through its environment, but comes down by the 
gradual subsidence of a whole column. This is generally brought 
about by the air at the bottom of the column spreading under 
the surrounding air. 

Thus it is essential for pupils to bear in mind that, nor- 

* The now recognized form of iso-entropic. 



METEOROLOGY AND WEATHER FORECASTING 321 

mally, air moves along an isentropic surface, and that ascending 
and descending currents are the exception. 

THE NEW AND THE QLD IDEAS. Formerly, all atmospheric 
motion was referred to tile ascent of warm air through cold air, 
and the descent of cold air through warm air. There was a per- 
manent circulation from the equator to the poles in the upper 
atmosphere, with a return flow in the surface or middle layers. 

The old idea was right to this extent that the potential energy 
inherent in masses of air at different temperatures must be the 
origin of the kinetic energy of the winds. The main question is, 
how does the change from potential to kinetic energy take place? 

Margules's work has led to an entirely new idea as to the 
method in which solar energy is converted into the kinetic 
energy of atmospheric motion. Instead of warm air rising 
vertically like the warm gases in a chimney, drawing air in 
at the bottom and delivering it at the top, two bodies of air, 
one warm and the other cold, are brought side by side\ the 
cold mass slowly subsides, and pushes its way as a wedge of 
cold air under the warm air which is partly raised and partly 
drawn in above to replace the cold subsiding air. In the pro- 
cess the centre of gravity of the whole moving mass is gradually 
lowered, so providing the energy of the motion which we 
recognize as winds. 

The essential difference between the new and the old ideas 
is that the two masses of air, in which the difference of tem- 
perature is the cause of the motion, do not mix. We start with 
two bodies of air side by side, with a surface of sharp discon- 
tinuity between them. In each body there is a different strati- 
fication of isentropic surfaces. In the warm body, the corre- 
sponding isentropic layers are all lower than in the cold body 
of air. There is a gradual adjustment to corresponding isen- 
tropic surfaces, but, in the process, the surface of discontinuity 
is a sliding surface, and no air crosses it. 

SURFACES OF DISCONTINUITY. The surfaces at which rela- 
tively cold and warm masses of air meet and slide over each 



322 SCIENCE TEACHING 

other can easily be recognized on meteorological charts and 
by observations in the upper atmosphere. On a stationary 
earth, a surface of discontinuity would rapidly disappear, or 
appear as a horizontal surface with alj-the cold air underneath 
and all the warm air above. Actually/we find inclined surfaces 
of discontinuity persisting for days together, and others which 
are apparently permanent. This arises from the effect of the 
rotation of the earth. Mathematical investigation shows that, 
on a rotating earth, the tendency of cold air to pass under 
warm air may be completely counterbalanced by forces due 
to the earth's rotation, 

Bjerknes considers that there are three great permanent 
surfaces of discontinuity of this kind in the atmosphere: (i) 
that between the troposphere and stratosphere; (2) that between 
the trade-winds and the anti-trade winds above them; (3) 
that forming the " polar front ". 

CYCLONES. The old hypothesis that a cyclonic depression 
is a kind of chimney drawing air in below and giving it out 
at the top can no longer be held. A cyclone was sometimes 
described as a cylindrical vortex, with its axis nearly vertical, 
rolling along at a rate conjecturally dependent partly on the 
tilt, and with an axial uprush of air to fill up a central depres- 
sion; this depression was nevertheless maintained and might 
be intensified by the whirl, the energy being derived from the 
condensation of vapour. If this were the true mechanism of a 
cyclone, we should expect to find a considerable amount of 
symmetry round the axis. The air would move in a continuous 
stream circulating round the centre but always approaching it; 
in other words, the stream-lines would be continuous spirals. 
There would also be little difference of temperature in the 
different parts of the cyclone, for the same air current would 
pass successively through all parts. 

In reality the conditions are entirely different. When 
stream lines are drawn by the aid of the wind arrows on synoptic 
charts, it is impossible to connect them so that they circulate 
all round the depression. On the contrary, they are discon- 



METEOROLOGY AND WEATHER FORECASTING 323 

tinuous, the stream lines in certain parts meeting the stream 
lines in other parts almost at right angles. There are also large 
discontinuities of temperature, each set of stream lines having 
its own temperature, further, it is found that the areas of 
rainfall are not confinedito the central regions, but are broad 
bands radiating from the centre like spokes in a wheel, showing 
that the ascending air is not taking place mainly in the central 
region. Whatever cyclones may be, they are certainly not 
homogeneous rotating systems. 

Bjerknes has given us much new knowledge of cyclones. 
We have to recognize that a cyclonic depression is the meeting- 
place of polar and equatorial air. Each body of air is stable 
to vertical currents within itself , but, where the two masses 
meet, readjustment is necessary; the surfaces of discontinuity 
tend to set themselves at the angle necessary for stability under 
the existing conditions of velocity and temperature. This 
involves the bodily raising of the warm air over the cold air, 
and a general sinking and spreading out of the cold air. The 
energy for the process is derived from the conversion of potential 
energy into kinetic energy as the centre of gravity of the air 
as a whole is slowly lowered during the readjustment of the 
air masses. The energy derived from the condensation of 
water-vapour is a very insignificant part of the energy developed 
in a cyclonic depression. But we still have much to learn 
about cyclones, and no hypothesis yet put forward to account 
for all the facts seems to have found general acceptance. 

Were there no water-vapour in the troposphere, the 
" digging out " from the stratosphere would be greatly reduced, 
and the stratosphere would be brought down much nearer the 
surface and would be interfered with only by such convection 
as belongs to dry air. In fact, if there was no water vapour, 
the working of the atmospheric engine would be much simplified, 
because the atmosphere would then be transparent both for 
the solar radiation by which heat is gained and for the terrestrial 
radiation by which heat is lost. The last word has not been 
said by a very long way, either about the atmospheric engine 
as a whole or about that particular part of it we call cyclones. 



324 SCIENCE TEACHING 

The Teaching of the Subject 

Meteorology is seldom taught except under the more 
general heading " climatology " taken as a branch of geography 
and not as a branch of science. It cy>es not therefore receive 
great attention, just about enough to enable pupils to answer 
examination questions on cyclones, monsoons, and the like. 
But the older books are full of hypotheses now discarded, 
and the " facts " taught sometimes convey notions which are 
demonstrably wrong. 

Is it desirable to teach the subject at all? 

The answer is in the affirmative, though it is undesirable 
to ask questions on it in examinations. A good deal of the 
subject remains at the conjectural stage, and even the now 
generally accepted hypotheses are difficult to explain lucidly, 
if only because some of the necessary facts are themselves 
rather obscure except to experts. Great caution must be 
exercised in handling the subject, even with a Sixth Form. 

Some of the best teachers in the past have attempted to give a 
foundation to the subject by analysing the conditions in this way: 

1. Consider all the irregularities of the earth's surface to 
be levelled down, and to be wholly land or wholly water (in 
order that all local atmospheric variations may be ignored), and 
consider the earth's axis to be perpendicular to the plane of the 
ecliptic. What would be the air circulation due to the spinning 
only? to the action of the sun only? to the two things combined? 

2. The same, with the earth's axis inclined? 

3 . The same as 2 , with the existing variation of water and land 
distribution, including the variation of height in the land forms? 

The idea is, of course, to consider the forces at work, one 
at a time. From a teaching point of view this is excellent, 
but the phenomena are vastly more complex than is here 
assumed. Such an analysis is based on the assumption that 
the meteorological data we can gather at the earth's surface 
are all sufficient, but it is now a commonplace that the data 
necessary must be obtained at all levels of the atmosphere, 
and we must frame our hypotheses in accordance with such of 



METEOROLOGY AND WEATHER FORECASTING 325 

these data as are undisputed facts. Even if the only factors 
concerned were a spinning earth and a blazing sun, it would 
be rash indeed to argue a priori that therefore the facts must 
be so and so. This may* be good philosophy but it is certainly 
bad science. 

Forecasting 

The kind of data accumulated every day by the meteorological 
office, the methods of obtaining it from permanent local stations 
and from ships at sea, and the construction and interpretation 
of weather charts, should be known by all senior pupils. The 
methods of exploring the upper atmosphere should also be 
known. But only a very general knowledge of the forecaster's 
art can be taught. To the expert the art has become simple 
enough, but to the layman it is difficult. 

The old method of forecasting was mainly empirical, and 
based on the work of Abercrombie. Abercrombie had sketched 
the distribution of weather about centres of high and low pres- 
sures, and forecasting was based on the determination of the 
movement of these pressure distributions where they appeared 
on the weather chart, the assumption being made that as the 
pressure system passed over a place the normal sequence of 
weather would be experienced. 

Now the forecaster knows more about the structure of a 
depression. The pressure distribution is, of course, still the 
main factor, but the forecaster searches his chart for indications 
of the surfaces of discontinuity, and examines the characteristics 
of the air masses to see whether they are of polar or equatorial 
origin. In this way he is able to determine the structure of 
the cyclone, and whether it is developing or dying. Having 
determined where the surfaces of discontinuity are situated, 
he is able to say where rain may be expected, and he knows 
what weather changes will accompany the passage of each 
surface of discontinuity as it moves over the surface of the 
land. He is aided in this by observations taken in the upper 
atmosphere by means of pilot balloons and airplanes fitted out 
with meteorological instruments. 



3 a6 SCIENCE TEACHING 

Concluding Remarks 

It would be difficult to criticize a teacher who decided that 
meteorology was an entirely unsuitable subject of science for 
inclusion in a school course, especi^ly if he argued that no 
experimental work is possible, and that lessons must be based 
on data accumulated by other people; that, in short, the 
teaching must be wholly deductive and didactic, and therefore 
be of less value than the teaching of most other branches of 
science. On the other hand, he might decide that an elementary 
knowledge of meteorology is now expected of all intelligent 
people, and that therefore a certain amount of time devoted 
to it would be usefully spent, even though the teaching would 
not be true science teaching. He might go further than this 
and urge that there are many other subjects which we cannot 
learn at first-hand, and that it is therefore useful for boys to 
learn how to use admittedly true facts obtained second-hand, 
and to examine hypotheses which have been framed in explana- 
tion of particular groupings of such facts. 

Geography teachers will probably be wise to follow Mr. 
Lempfert's order of treatment of the subject. The earlier 
chapters in his Meteorology deal with " weather maps ", pres- 
sure, winds, temperature, clouds, and relation of winds to 
pressure distribution, chapters which show how available 
meteorological records are made and what deductions may 
safely be drawn from them. As the book develops, it becomes 
less elementary, and only a teacher well versed in physical 
science is likely to cope with it properly. 

Teachers desiring to take up this difficult subject seriously 
must consult Sir Napier Shaw's Forecasting Weather, Manual 
of Meteorology (2 vols.), and The Air and its Ways, books too 
difficult for school use, but necessary for teachers of meteor- 
ology to read. An excellent introduction to them is Geddes's 
Meteorology. A good recent German standard work is Wetter 
und Wettervorhersage (Synoptische Meteorologte) by Dr. Albert 
Defant. Anything written by Dr. G. C. Simpson, the present 
Director of the Meteorological Office, is always illuminating. 



PART III 

EXTENDED CONSIDERATIONS FOR SIXTH 

FORMS 

A Sixth Form is a Form doing work beyond School Certi- 
ficate stage, and such work ought to be something more than 
the continuance of the same type of work previously done. 
Sixth Form boys ought to begin to weave together the threads 
drawn from different subjects, and get some idea of science as 
a whole. They ought to know something of, e.g., the work on 
which so many of the world's great physicists have been con- 
centrating for years the constitution of the atom; and this, 
in its turn, means fairly advanced work in physics and astro- 
physics, and chemistry. They ought to have a good all-round 
knowledge of elementary biology. They ought also to know 
something about the foundations of science, and have some 
elementary notions of the philosophical implications. The 
work done should be work for the majority, those who com- 
plete their education at school. Those who pass on to the 
university will naturally have greater opportunities, for seeing 
things in a proper perspective, than can be given at school. 

One or two of the newer universities are still preparing 
students for the so-called " Intermediate " examinations, appa- 
rently failing to recognize that work of this grade has now 
become the staple diet of the First Year of the Sixth Form, 
as indeed it already has been for many years past both in our 
own Public Schools and in schools on the Continent. The 

327 



328 SCIENCE TEACHING 

complaint is made by representatives of those universities that 
such work cannot be digested by boys of 17! Still, Sixth Form 
teachers of science should remember that if they entrench 
themselves behind such a syllabus as ,the Intermediate exami- 
nation syllabus, they do run the risjt of being charged with 
incompetence. If Sixth Form work is of a mere memory- 
clogging character, the exacting intellectual discipline which 
is the first essential during these two years will take a second 
place, and the university critic will then not be slow to seize 
his opportunity. 



CHAPTER XXX 

Sixth Form Work and its Critics 

Sixth Form work of the present day tends to follow the 
broad lines of the Board of Education " Advanced Courses ", 
and in science this means that from two-thirds to three- 
quarters of the school time is devoted to science subjects and 
(generally) mathematics. The usual plan is for two science 
subjects to be included, and commonly these are either chem- 
istry and physics or chemistry and biology. The remaining 
time is given up to English and other non-science subjects. 

One critic of this work utters his complaint in this way: 
" Those pupils who show any aptitude for science are mostly 
led, for the last two years at school, to tread the path of speciali- 
zation on their journey to the universities. They arrive at the 
universities embryo chemists, physicists, or botanists where 
they are hatched out as full-fledged specialists destined to act 
as guides to others along the same narrow paths, or to apply 
their specialized knowledge to industry. The revolt against 
the old-fashioned classical education was successful because 
the teaching of the classics had become so specialized that the 
main object of the study was obscured. It encouraged the 
worst forms of pedantry. There is abundant evidence that 
the teaching of science is suffering from the same disease. The 
spirit of science, the systematic observation of facts, the con- 
ception of hypotheses, to be discarded if they cannot be verified 
over a complete range of observations, or enunciated as uni- 
versal if they stand such test, the constant challenge to estab- 
lished precedents or authority, is apt to be obscured by a mass 
of technical trivialities which passes for scholarship/* 

329 



330 SCIENCE TEACHING 

Another writer says: " Many university teachers are 
seriously disturbed by the obvious growth of specialization in 
the schools, and especially by the results of such teaching on 
the mental outlook and capacity of university entrants. It is 
not true to say that education is general to the age of 16, and 
that specialization only appears after that age. Specialization 
has a sinister tendency to creep downwards." 

These criticisms are not just, though there is some small 
measure of truth in the first. The country considered as a 
whole, education up to the School Certificate stage is most 
certainly general and not specialist. There is this difference 
between secondary education of the present day and that at 
the public schools thirty or forty years ago: then, the work 
was nearly always specialist, sometimes even in the Preparatory 
schools, and classics was almost always the subject in which 
specialization took place; but at the present time education 
is quite general up to the Fifth Form (School Certificate 
stage), though in some measure it is specialist in the Sixth. 
This Sixth Form specialization is kept within bounds; the 
basis of the work done is very much broader than the sub- 
sequent university work. It is rightly argued that the Sixth 
Form boy ought to have to wrestle with serious intellectual 
difficulties, whatever branches of knowledge be chosen for 
the purpose, and not to devote his time to the same grade of 
work that characterized his pre-sixteen education. Speciali- 
zation in the correct sense of the term does not usually now 
begin until the boy reaches the university. There is another 
important point: schools have to provide courses of instruction 
for the majority, not for the minority that proceed to the 
university, and specialization for that majority is wholly un- 
necessary. 

It is, however, quite true that boys working for university 
scholarships in science have to face the drudgery of reading 
up masses of indigestible stuff for the purpose of answering 
questions on obscure points of detail: that is the fault of the 
university authorities, not of science teachers at the schools. 
And some of the questions asked in Higher Certificate papers 



SIXTH FORM WORK AND ITS CRITICS 331 

are unsuitable; they presuppose a knowledge of the technical 
minutiae of, say, organic chemistry, or of mathematical physics; 
and the time devoted to the teaching of this sort of thing is 
certainly wasted. But here, again, it is not the fault of the 
science teachers but the ^ult of examiners who do not under- 
stand their job. 

A leading science master wrote to Nature (24th March, 
1928), saying that he had looked through a few chemistry 
papers set recently at one group of Cambridge colleges and had 
found questions on (i) the alloys of mercury and potassium; 
(2) ionic transport numbers; (3) the manufacture of lithopone; 
(4) the synthesis of dimethylacetic acid. Comment on this 
calls for strong language. If such questions are set, how can 
science teachers be expected to adopt rational teaching methods? 

Another critic has said: " The years 16 to 18 should be a 
breathing-space between the School Certificate examination 
and the commencement of university studies; they should 
provide a period of wide reading rather than intensive study 
of a restricted syllabus, a period for * browsing ', for the enjoy- 
ment of poetry and art, for leisurely thinking." Does that 
critic seriously urge that the years 16 to 18 should be devoted 
to lotus-eating? Would he argue that it is unnecessary for boys 
at that critical age to wrestle with serious intellectual problems, 
for instance, to read science in such a way as to be compelled 
to get to grips with the relation between cause and effect? 
that, instead, they should devote their time to making a super- 
ficial acquaintance with natural phenomena catching butter- 
flies and blowing soap-bubbles and writing odes to the Queen 
of Mars? No. Sixth Form boys must be taught to work. 

There is, however, one very important feature of Sixth 
Form science that calls for really serious criticism, and that 
is that the prescribed course of w r ork is not liberal enough. 
At the very least, a general course of biology should be included 
in the course, be the more substantive subjects what they may. 
This does not mean that any part of the course should be 
allowed to become intellectually less exacting. The necessary 
time for the new subject may be found by cutting out of the 

( K 72 ) 23 



332 SCIENCE TEACHING 

chemistry, physics, and mathematics courses all unnecessary 
" frills " technicalities which are of no importance to any- 
body save the specialist. 

Any Sixth Form course must be so designed as to demand 
close attention and close application^ The training in method 
must become more and more severe; the scrutiny of facts and 
of hypotheses must become more and more critical. Reason- 
ing will sometimes have to be carried far ahead of basic prin- 
ciples, but it must always be traceable back to them. There 
must be no weak links in chains of reasoning. 

Another essential feature of Sixth Form work is that pupils 
should be fully conscious that a lesson is sometimes gathering 
into its ambit knowledge previously obtained from several 
subjects. The reasoning employed will thus depend on a clear 
grasp of the relations of many facts obtained from different 
sources on different occasions, facts which hitherto have seemed 
to have no obvious relations at all. If any of this old work 
has been imperfectly done, revision is essential, or the new 
work will be valueless. We outline subject-matter for a short 
series of lessons on two new subjects: (i) the structure of the 
atom, (2) relativity. Each subject will call for, by way of an 
introduction, a good deal of revision of old work, and this 
necessary old work we summarize. 



CHAPTER XXXI 

The Structure of the Atom 

The first five sections of this chapter contain brief outlines 
of a necessary revision course: it is assumed that the pupils 
have already taken courses in physics, including mechanics 
and elementary spectroscopy, and have some knowledge of 
radioactivity and astronomy. Some of this work will probably 
have been done in the first year of the Sixth Form course. 
The sequence of topics adopted is found to work well in practice. 



THE STRUCTURE OF THE ATOM 333 

Astronomical Considerations 

Angular momentum mr 2 a>; acceleration towards centre 
= o> 2 r; centripetal force = mv 2 /r. 

Since r 3 oct 2 (Keplej-'s third law), it follows that rv 2 is 
constant for all orbits round a single attracting centre. 

The orbit of a projectile is curved; it is a parabola (really 
an elongated ellipse). The original impulse given to the moon, 
is enough to keep it falling back to earth. 

For centripetal force necessary to curve the path into a 

circle, mv 2 /r = mg (weight), or v = x/#R = y 3 ~ - * - 

5 (miles a second). 3 7 

Shell fired at 5 miles a second (300 miles a minute) (if 
beyond obstruction of earth's atmosphere) would become a 
moon with a period of ^ hours. If velocity less than this, 
it would hit the earth sooner or later. If 300 x/ 2 or more 
miles a minute it would go off to infinity. 

Body falling from infinite distance: under 
inverse square law, v (on reaching earth) 

v 2#R. This same velocity would enable 
the body to get away to infinity; it is equal 
to x/2 times the speed necessary for rotation. 

Kinetic energy acv 2 , and is written ^mv 2 . 

Hence, energy acquired by a body falling from infinity = mgR. 
This energy which a body must possess to enable it to revolve 
round the earth = \mg& " the energy that would be acquired 
by a free fall through a height equal to half the radius of the 
earth, whereas the energy from infinity, or ESCAPE ENERGY, = 
the free fall under uniform gravity through a height equal to 
the whole radius. 

The moon as an example. Here, distance is 60 times earth's 
radius. Hence speed of moon in its orbit is $/ \/6o miles a 
second; speed of escape is 5 ^/2/ x/6o miles per second. Thus, 
if the moon could be given an extra push, to make it travel 
about half as fast again, it would bid the earth a final good- 
bye. 




334 SCIENCE TEACHING 

ENERGY needed for escape is just double the energy required 
for circular revolution. Thus if the revolution energy of any 
planet were doubled, it would escape control and fly away. 

(All this is of great importance in the consideration of 
electronic orbits.) 

The Periodic Law 

Mendelieff's and Newlands's work: if the elements be 
arranged in a table in ascending order of atomic weights, the 
elements with similar physical and chemical properties appear 
at recurring intervals. The nuclear theory of the atom gave a 
new insight into the origin of these properties. 

The properties are of two independent classes: (i) those 
(ordinary physical and chemical properties) depending on the 
constitution of the cluster of revolving electrons; (2) those 
depending on the actual internal structure of the nucleus 
(radioactive properties). 

That the two sets of properties are independent is shown 
by the existence of substances indistinguishable from one 
another by any ordinary physical and chemical tests, but 
whose atomic weights differ and whose radioactive properties 
differ. These isotopes occupy the " same position " in the 
Periodic Table. In 1913 Soddy suggested that atoms might 
differ in weight but in no other particular; this was verified by 
Thomson and Aston. 

Radioactivity 

Kinds of Radiation. How demonstrated: 

-rays: how identified as He atoms; +' y charged particles 
/2-rays: considered as cathode rays consisting of electrons, 
y-rays: X-rays of very short wave-length. 

Nuclear Nature of the Atom. The massive nucleus of an 
atom consists of two distinct parts: (i) an inert mass of inactive 
protons and electrons; (2) a number of charged protons. The 
latter hold an equal number of electrons together, into a sort 
of solar system. 



THE STRUCTURE OF THE ATOM 335 

Atomic weight = total number of protons. 

Atomic number = number of active protons (usually about half 
the total). 

Electrons and protons are and + units of electricity. Relative 
weights, i : 1830. All protons assumed to be alike; so all electrons. 

Evidence, direct and inferential. Rutherford's method of 
bombarding N atoms (each containing 14 protons); 2 protons 
flung out violently as atoms of H; the other 12 hung together 
in groups of 4, as atoms of He. But we may not infer that N 
consists of 3 He and 2 H atoms, though the N nucleus must 
contain H in some way. 

Are all elements built up of H atoms? 

Atomic weight of He 4. If H i , we should feel pretty 
sure that He is built up of 4 atoms of H. But H 1-0077. 

Hypothesis. Every electric charge has a certain mass 
associated with it, and the inertia of matter is due to a magnetic 
field of moving electric charges. But if + and charges are 
packed very closely together, the combined inertias are less than 
the sum of the separate inertias, because of the tendency to neutra- 
lization. Some of the mass will have disappeared. Thus if the 
He nucleus consists of 4 atoms of H, they must be packed tightly 
together, with a resulting diminished mass from 1-0077 X 4 to 
1X4. H in combination is i; free, 1-0077. Thus He and all 
other atoms may be composed of H, but of tightly packed H. 

Wilson's experiments and photographs. Inferences therefrom. 

Collect the results of the experimental work of Rutherford, 
Thomson, Wilson, and others and show how converging lines of 
evidence all point to the main hypothesis: every atom has a 
central solid compact nucleus, positively charged, round which 
negative electrons revolve, according to the inverse square law. 
Thus the atom seems to be a miniature astronomical system. 
If this be so, the problem is, does this system obey the 
ordinary laws of dynamics? 

How e (the fundamental electrical unit) and m (mass of 
electron) are determined. By experiment we know m/e, v, 
nev, and n. These data are enough to determine and to verify 
and m. 



336 SCIENCE TEACHING 



^therial Radiation and Wave Measurement 

The history of spectroscopy. Different kinds of spectra: 
the ever-increasing complexity in nurpber of lines. Detection 
of order and law amongst the lines: a definite series belongs to 
each element. The H series the simplest. Characteristics of 
the series. Repetition of similar series in the infra-red and 
ultra-violet. How these series differ and how they are alike. 

What the lines represent: waves of definite length and 
frequency. 

How wave-lengths are measured. Wave-length compared 
with dimensions of diffracting aperture. Diffraction grating 
more effective than diffraction slit (A = d sin0). But the 
dimensions of even the best grating are too coarse for the 
measurement of X-rays. Laue's discovery of the use to which 
space-structure of crystals may be put; the X-ray spectrometer. 
Photograms and their interpretation. 

How all setherial waves are alike: same velocity, all subject 
to same laws of refraction, reflection, polarization, interference. 

How all the waves differ: only in frequency and length. 

For all waves, v = nX; v and A can be measured; hence 
n is known. Wave-length expressed in Angstrom units (A.U.) 
= io~ 8 cm. = i/io/xft. Spectral lines represented by wave- 
numbers, obtained by dividing io 8 by wave-lengths.* 

Radiation at its source due to changes in velocity of elec- 
trons. 

Present knowledge of electromagnetic radiation extends 
over a range of 70 octaves (wave-lengths, -ooi A.U. to 10,000 
km.). The B.B.C. uses 2 octaves. Visible spectrum extends 
over i octave (3900 to 7600 A.U.). 

The Hydrogen Spectrum 

The best known lines in the H spectrum are the three dis- 
covered by Fraunhofer as black lines in the solar spectrum; 

* See pp. 293-4. 



THE STRUCTURE OF THE ATOM 337 

the one in the red he labelled C; the one in the greenish blue, 
F; the one in the indigo, G. We now call then B, C, and D 
respectively, and we know a fourth well-known line E, as well 
as a number of fainter lines crowded together and finally 
coming to a limit in the form of a " fade-away ", and termed 
Z. Then we think of the series as B, C, D, E, . . . , Z. The 
series itself is called the " L " series. It is the one series in 
the visible spectrum. There is a similar series (K) in the 
ultra-violet, and still others (M, N, O) in the infra-red. In 
each series the same letters (B, C, D, E, . . . , Z) are used to 
distinguish the spectral lines, though not all the lines appear 
in the various infra-red series. Make blackboard sketches to 
show the relations of all these lines. See figs. 3 and 4. 

The Balmer Formula 

This subject is best introduced by giving the boys a " series " 
of numbers from which they have to discover the general term. 
They will have had some experience of this in algebraic series. 

For instance, the general term of the series i, J, J, ,V> ... is ~ v 

n* 

Such a series may be masked; e.g. 3600, 900, 400, 225, 144. 

Obviously the general term is o X 3600, and the 3600 may 

n~ 

conveniently be called a constant. 

Hagenbach measured the wave-lengths of the 5 principal 
H lines in the visible spectrum. The results were: 

6563-04 
4861-49 
4340*66 
4101*90 
3970-25 

But he could not find the general term, or, indeed, any relation 
amongst the numbers. He handed over the problem to Balmer, 
an assistant master in a Basel secondary school. After many 
trials, Balmer found the constant, viz. 3645-6, since called the 



338 SCIENCE TEACHING 

" Balmer constant " and written " B ". Here is the solution 
he gave to Hagenbach. 

6563-04 = B x 1-8 = B x -? = B x ? = E( - 3 * } 

\3 2 - 2 2 / 

4861-49 = B x 1-3 = B x $ = B x ] = E(~^-~- \ 

\4 2 2 2 / 

4340-66 = B x 1-190476 = B x if = B X if = B^-^- 2 

4101-90 = B x 1-125 = B x S : = B x M = B(" 

\6 2 z 

3970*25 = B x i-oS = B x 1? = B x fj = Bf^-l 2 -- -) 

\7 2 2 2 / 

Thus the general term is B( ~ ); that is, the wave- 
length, A, is ^ 2 - 2 '/ 



where n represents the natural numbers 3, 4, 5, 6, 7. 

If frequencies (reciprocals of lengths, since v = nX) had 
been given, a formula could have been found just as easily. 
The five numbers in the first column below represent the 
frequencies corresponding, respectively, to the five wave- 
lengths above. In this case the constant is 109678, now called 
the " Rydberg constant " and written R. 



15241 = R x -138 = R x & = R(i ~ IT) - R(- - ~ 

\2 2 3 2 

20575 = R x -1875 = R x ft = R(} - A) - Rf-- 2 - ~ 

\2 2 4 2 

23044 = R x -2i R x rffe - R(i - A) - Rf-. - 

\2 2 5 2 

24386 = R x -2 - R x f - R(l - A) = Rf 1 - - 

\2 2 6 2 

25194 = R x -23 = R x ts = R(J - A) = Rf- a - i 

\2 a 7 2 



THE STRUCTURE OF THE ATOM 339 

Thus n (wave-frequency) R (-), 

\2 2 n 1 ) 

where n represents the natural numbers 3, 4, 5, 6, 7. 

/ n 2 2 2 \ 

Note that the formuL may be written R ( ). Com- 

/ W 2 \ \ 4" 2 / 

pare this with B I -- 1 above. Evidently B 4/R. 

\n 2 / 

The constant might have been written 4R instead of R, and 
would then have been the reciprocal of B. But R is now an 
important constant in other connexions. Slightly different 
values are given to it by different authorities. 

(The units used do not affect the general result.) 

The Grouping of the Different Hydrogen Series 

Here is a diagrammatic view of the successive Hydrogen 
series in the spectrum. The L series is in the visible spectrum. 



Ill 


I 


il 






III S Al 


3 ( X5 


II 


E Z 
O 

cries 

v 


D E Z C D E Z B { 

N M 
Series Series S 

j 


: D E z 

L 
cries 

isible x 
;ctrum ' 


A B C D E Z 

K 
Series 

( Ultra-Violet ) 


Infra- Red 


/ V 

I Sp< 



Fig- 3 

The L series in the visible spectrum was the first discovered. 
When the other series were discovered, they all seemed similar 
to the L series. The wave-lengths were measured: did they 
square with the Balmer formula? These points should be 
noted: 

1 . The first (or K) series is far up in the ultra-violet. 

2. The second or original Balmer (or L) series is in the 
visible spectrum. 

3. The third, fourth, and fifth series (M, N, O) are in the 
infra-red. 

4. The " head " of each series is a fade-away called Z. 



34<> 



SCIENCE TEACHING 



5. The other end of each series is called the " fundamental ". 
The fundamental of the K series is called A; of the L series,. 
B; of the M series, C; and so on. 

6. The first and second series are a long way apart, about 
5 times the length of the distance ^.B. 

7. The K series less the A line gives the L series; the L 
series less the B line gives the M series; and so on. 

8. The spacing between the lines (between C and D, for 
instance) seems to be the same for all. 

Ritz tried a modified formula o . giving different 

m" rr 

values of m to the successive series (values of n as before). 

Writing it in the form B ( ) , he gave B the arbitrary 

\m? n 2 / 

value 900. This merely affects the scale, of course, and not 
the relative values. 



Lines, and 
Values of n. 


Series, and Values of m. 


Interval 
Differ- 
ences. 


K; i 


J-; 2 


M; 3. 


N; 4 - 


0; 5. 


A; 2 


1 08 











i 


B; 3 


128 


20 


O 








} 20 

I 1-1 


C; 4 
D; 5 
E; 6 


135 
I38'24 
140 


27 
30-24 
32 


7 
10-24 

12 




3-24 

5 


O 
I- 7 6 


I 7 
} 3*24 
} 1.76 


Z; oo 


144 


36 


16 


9 


5 : ?6 






In the above table, let the pupils note carefully: 

1 . The relatively large values of the frequencies in the K 
and L series, and the consequently relatively long distance 
apart of these series in the spectrum. 

2. The intervals between the corresponding lines, shown 
in last column, are actually the same in all the series, as appear- 
ances led to believe. 



THE STRUCTURE OF THE ATOM 



34 1 



3. The intervals diminish as n increases. 

4. The head (Z) of each series is the same distance from 
the corresponding lines. 

5. The intervals in each series are identical except that: 
(i) they occur in different absolute positions; (2) an earlier 
series has one fundamental line on the left more than the 
next later series has. Thus only the K series has line A. 

6. m fixes the number of the series; n m fixes the number 
of each line in the series. 

It is now easy to see that if a spectrum is cut up, the series 
will fit exactly over each other thus: 



E I 
2 6 



E I 

3 5 9 



C E Z 

7 10 12 IG 



B C E Z 

20 27 30 32 3G 



1 ' 






INI 


A B 

103 128 


C D E Z 

135 136 140 144 



Fig. 4 



The infra-red series beyond the O series are ignored, 
practice even the O series is generally ignored. 



In 



Bohr's Interpretation 

Bohr suspected that there was some intimate relation 
between these series of spectrum lines and some sort 
of astronomical model, and he asked himself how he could 
reconcile the two following apparently antagonistic facts: 



342 SCIENCE TEACHING 

1. According to the Ritz law (the generalized Balmer law) 
the frequencies of vibration of successive lines in the spectrum 
are represented by the difference of the reciprocals of the 
squares of the natural numbers. 

2. According to the law of gravitational orbits, the energy 
of a planet is proportional to the reciprocal of the radius of 
its orbit. 

Bohr applied the quantum theory to Rutherford's astro- 
nomical model of the H atom, and he postulated that, although 
any planetary orbit round the sun is conceivable (depending 
merely on the original impulse with which the planet was 
originally shot forth), there could be only specific orbits for 
electrons, the radii of these proceeding as the squares of the natural 
numbers. This granted, everything else followed. 

When considered astronomically, the postulated succession 
of orbital radii as the squares of the natural numbers, requires 
that the rate of sweeping areas, or the moment of momentum, 
of an electron revolving inside the atom, is a quantity that 
proceeds by indivisible steps from one orbit to the next, and 
that energy is emitted only when an electron jumps from orbit 
to orbit. For if r oc w 2 , then vrocn (Kepler's third law). This 
is expressible by saying that the moment of momentum is 
an integer multiple of some atomic unit. 

Each orbit must have a characteristic rate of revolution, 
and, as in astronomy, an electron in a smaller and inner orbit 
must have a greater velocity than an electron in an outer. 

The innermost orbit, called the K orbit, is a one-quantum 
orbit. The velocity in it is 1/140 the velocity of light, and 
the revolution number = 6000 X io 12 per second. In this 
orbit we have the highest frequency and shortest wave-length. 
It is the most stable orbit, and the H electron is normally in it. 

The next orbit, the L orbit, is a two-quantum orbit. Then 
follow the M and N orbits, farther and farther from the 
nucleus; and still other orbits beyond, which may be ignored. 

By sudden excitation from without (heat-motion, collision, 
electric-fields, cathode-rays, X-rays, &c.), an electron is appar- 
ently jerked out from an inner orbit into an outer orbit, but 



THE STRUCTURE OF THE ATOM 343 

it men has less stability. Left to itself, it jumps back sooner 
or later into some inner orbit. During this jump back, energy 
is liberated, and is emitted in the form of mono-chromatic 
radiation, i.e. radiation of one wave-length. Only during these 
transitions is the light-energy radiated. The energy emitted 
is the difference of the ehergy in the initial and final orbits. 
The frequency of the spectral lines produced by the transition 
is thus determined. 

Thus every spectral line is produced by an electron jumping 
from one orbit to another. The particular rate of vibration 
depends both on the orbit jumped from and the orbit jumped 
into. A study of the spectra enables us to specify these two 
orbits. 

An electron revolving steadily in an orbit does not disturb 
the aether. But a jumping electron gives a sort of kick to the 
aether and sets up a wave. The frequency of this wave depends 
on the violence of the kick, i.e. on the energy liberated. 

To excite K radiation and to produce K lines, an electron 
must be jerked from the K orbit either into an outer orbit or 
away to " infinity " (a relatively great distance). The K " shell " 
of electrons (only I in H) tries to complete itself again, and the 
missing electron may be furnished from the L, or the M, or 
the N, or any other orbit. Whereas the process of excitation 
was accompanied by a gain of energy, the converse process 
takes place with loss of energy. According as the missing 
electron returns to the K orbit from the L, M, or N orbit, 
the energy set free will be different in amount. Hence there 
will be various possible K radiations, each of them represented 
by a definite wave-length, and all of them together giving the 
K series of lines. The K series occur high up in the violet. 

To excite L radiation, an electron must be jerked out of 
the L orbit into an outer orbit. The L lines are the original 
Balmer series and occur in the visible spectrum. The charac- 
teristic red line (Fraunhofer C) is produced by a jump from 
the M orbit to the L orbit; the blue line, by a jump from N 
to L. 

And so on. 



344 



SCIENCE TEACHING 



The series, and the positions of lines in series, are thus 
determined: 

1 . The series is determined by the orbit into which electron 
jumps. 

2. The lines in a series are determined by the orbit from 
which electron jumps. 

3. The fundamental (lowest) line of a series represents a 
jump from the next orbit. 

4. The head (highest) line of a series represent a jump 
from " infinity ". The results may be shown diagrammatically, 
thus: 




Fig. 5 



Since each series is connected with one orbit, why is there a 
series of lines instead of only one line? If electrons all jumped 
from the same outer orbit into (say) the L orbit, their radiation 
would consist of only one line. But if the H is strongly agitated, 
electrons will probably be jerked into many of the outer orbits; 
hence the jumps back represent different energies, different 
frequencies, and different lines. We are always dealing with 
many H atoms, not with only one. 



THE STRUCTURE OF THE ATOM 345 

Energy Considerations 

The different orbits are characterized by different energies, 
which are inversely as the radii. Thus the frequencies of 
vibration characteristic of the different jumps are all different. 

An electron falling inwards under electrical attraction loses 
potential energy and gains kinetic. The latter is twice that 
required for revolution in a circular orbit at the given position. 
Hence it gets rid of the other half by radiation. It is a remark- 
able thing that half the kinetic energy possessed at a certain 
stage suddenly goes away in radiation of a definite frequency, 
depending on where it has come from and where it has got to. 
This discontinuous behaviour has not been explained. 

If nucleus is charged with +E, and an electron with <?, 
the force of attraction at any distance r is Ee/2r, and this con- 
stitutes the centripetal force mv z /r y i.e. %mv 2 = Ee/2r. The 
additional energy to be given to the electron to enable it to 
escape is also Ec/zr. Hence energy of escape ~ Ee/r. It is the 
energy which it could have acquired by falling into its position 
from infinity. 

If the additional energy given to a revolving electron is, 

(1) as much as it already possesses, it flies away to infinity; 

(2) less than this, but equal to a critical value, the electron 
changes its orbit; (3) less than the critical value, nothing 
happens. 

Since the radii of the orbits are represented by square 
numbers, the total energy corresponding to each orbit (which 
we know to be inversely as the distance) will be represented by 
the reciprocals of the square numbers. Thus, if the total energy 
associated with the K orbit is i , that in the L orbit is J. Hence 
the step or difference in the energy from K to L is f ; from K 
to M, f ; from L to M, ^V; and so on. The energy in orbit 
N is tV hence to make an electron jump from K to N, f of 
its energy must be supplied to it. (A very little more would 
make it escape altogether.) And that is the amount of energy 
that will be emitted when the reverse step is taken. 

If the orbits are represented by horizontal lines, the energy 



SCIENCE TEACHING 



differences between the levels are easily indicated. In the 
succession of energy steps, the difference in height between 
two steps shows the energy liberated when an electron jumps 
from a higher to a lower step. 

For lines of a series to be emitted at all, there must be 
electrons in the jumping-off orbit, if very few of the atoms 
contain such electrons, the corresponding lines will be faint. 



o -_- 7 








t 




IN 








' 




:..' 


^ 


^totfe 


N 








1' 


tfz 


I 




JMc 




"jMd 




" 


- 




M 






Lz 






















k | 














Lb 




Lc 




Ld 








r/3e 


L 










\ 


f 


i 














1 




K. 




K, 




Kb 




K 


c 


K ( 


i 


I 




* 





K ' 












i 


r 

















To Energy 
level of nucleus 



Fig. 6 



It was Planck who saw that the connexion between the 
radiating atoms and the energy they emitted could not be 
accounted for by any theory of continuous emission. Either 
definite portions of energy are emitted or none at all. Regu- 
larity and law remain, but everything takes place in steps y 
m gushes. The steps are not equal. Planck's quantum is a natural 
constant, accurately measurable. It is associated with the 
angular momentum of the revolving electron. 



THE STRUCTURE OF THE ATOM 



347 



For the interior of the atom, the older dynamics is still 
effective but requires supplementing, the phenomena being 
almost independent of such ordinary physical conditions of 
temperature and pressure. 

Moseley's Discovery 

Moseley photographed the X-ray spectra of different ele- 
ments. To produce the spectra, the elements were successively 
fixed into the X-ray bulb as anti-cathodes, and thus the charac- 
teristic rays were excited directly by means of cathode rays. 
By varying the fixed position of the crystal, he contrived to 
establish the region of wave-lengths for the prominent K series. 
The measured wave-lengths of the K lines for seven elements 
are shown in the second column of the following table. 

/ wave-length, n frequency. Since frequencies are 
inversely as wave-lengths, n~ i/l. R = the Rydberg-Ritz 
constant (the universal wave-number). 











Differences 






11 






Elements. 


/ (K Series). 


R' 


' 


ofV 


Na 


11883-6 


76-683 


8-759) 










/ 


853 


Mg 


9867-75 


92-348 


9-610, 










I 


856 


Al 


8319-40 


I09-535 


10-466 | 










t 


856 


Si 


7109-17 


128-182 


11-322' 










[ 


859 


P 


6141-71 


I48-374 


12-181 










> 


857 


s 


5360-66 


169-992 


13-038 










) 
f 


859 


Cl 


472I-85 


192-99 


1 3-897 - 





Similar results are obtained with all the other series, and 
with all the other elements, within the limits of experimental 
error. (The ratio n/R is a convenient number independent of 
the units of measurement.) 

(K72) 24 



348 SCIENCE TEACHING 

Thus the amazing discovery was made that the 92 elements 
may be arranged in order in such a way that the square roots 
of the frequencies of the corresponding spectrum lines form 
an A.P. If we multiply ^/n by such a constant as to bring 
the common difference to unity, we get the series of atomic 
numbers 1-92. Thus the different elements in the atomic 
series climb the ladder of frequency by regular and equal 
steps. 

Other points demanding the pupils' careful attention: 

1 . The atomic number gives the total number of active 
protons in the nucleus, also the number of revolving electrons. 
The number is more immediately vital to chemistry and spectro- 
scopy than is the atomic weight. 

2. Reconsideration of the Periodic Law. The significance 
of the grouping of the 92 elements: the periodic numbers 
2, 8, 8, 18, 18, 32, 6. " Shells " of electrons. Valency. 

3. Stability of atomic systems. 

(Further selected passages from Lodge's Atoms and Rays 
and from Sommerfeld's Atomic Structure and Spectral Lines 
might now be given to the more mathematically inclined boys 
of the Sixth Form.) 

A Necessary Warning 

The astronomical model of the atom has been presented to 
us with such extraordinary vividness, and it co-ordinates the 
facts of spectroscopy in such a remarkable way, that it is diffi- 
cult to bring ourselves to believe either that the picture is 
conventional and purely hypothetical or that it is extremely 
unlikely to be in harmony with reality. The hypothesis has 
proved wonderfully fruitful, not because we have succeeded 
in identifying the particular capers cut by the electrons in the 
atomic gymnasia but because of the numerical relations it 
includes. Most of the actual evidence that gave rise to the 
hypothesis consisted of mere records of scale readings from 
instruments. That electrons actually exist and that their approxi- 



THE STRUCTURE OF THE ATOM 349 

mate dimensions are known, there is hardly any room left for 
doubt. That one element differs from another in the number 
of electrons within the respective atoms is also a matter of 
reasonable certainty. But the planetary picture? No. The 
picture is just a pretty* analogy borrowed from astronomy, 
and pupils should be advised not to assume that it is really 
anything more. 



CHAPTER XXXII 

Relativity 

Why Beginners find Relativity so Difficult 

Inasmuch as relativity is transforming our fundamental 
notions of physics, and therefore of science generally, it is 
desirable that at least an outline of the subject should be pre- 
sented to Sixth Form boys. Mathematical considerations will 
necessarily be confined to the few boys of the Sixth Form 
who are specializing in mathematics and physics, and if these 
are going on to the university, the subject should be taken up 
seriously, though certain of the mathematical aspects of the 
" general " theory are much too difficult for inclusion in a 
school course and, indeed, form a tough morsel at the university 
itself. 

The real trouble with beginners is their reluctance to 
throw on the scrap-heap certain ideaS which hitherto have 
seemed to them logical necessities of thought space and time 
as independent things; gravitation as a " force ", and a force 
of attraction at that; the aether as something with a great 
density, even a calculable density; mass and energy as separate 
and distinct things. Until a boy is willing to surrender his 
old ideas, and to set to work anew, he will undoubtedly feel 
hostile to the new subject. He must give up the old notion 
that space bears no responsibility for anything that may happen 
in it. 



350 SCIENCE TEACHING 

The best books for beginners are Professor Rice's and Mr. 
Durell's, both simply written and easily mastered in a very 
short time. These may be followed by the greater part of 
Professor Einstein's own elementary book (The Theory of 
Relativity), a little book of 128 pages containing the essence 
of the whole subject, put in as simple a form as the difficulties 
permit. Under guidance, selections from Professor Nunn's 
and Professor Eddington's books may then be read. Nunn's 
book is a model from the teacher's point of view, but the 
mathematics of the latter part of it is beyond the reach of 
most school boys. The easier parts of Eddington's book should 
be read by every boy who intends to take up a university 
course in mathematics or physics. 

The following is an outline, with occasional comments, of 
a course of lecture-lessons given, with considerable success, 
to a class of Sixth Form boys who had been well grounded in 
mathematics and physics. 

Before Einstein 

The following ground must be covered (much of it will, 
of course, be revision), before the subject of relativity can be 
understood. 

Relative position and relative motion. Nothing in absolute 
rest. Fallacious inferences from sense-data. A New Zealander 
says England is " down under ": justification. The baffling 
complexity of astronomical movements: planetary orbits 
loops, cycloids, circles, or ellipses, and why. The lunar orbit 
round the sun: why a looped or sinuous path is not possible. 
Absolute and relative space and time. 

Newtonian mechanics. Laws of motion; inertia. Study of a 
falling body in a lift ascending and descending with uniform and 
with accelerated motion. 

Newtonian gravitation. Newton's deductions from Kepler's 
laws. His own law of gravitation and how he was led to for- 
mulate it and how he verified it. Any convincing reason why 
the attraction falls off exactly as the square of the distance? 



RELATIVITY 351 

Simple harmonic motion. Study of the pendulum. Variation 
of g. Centripetal acceleration and tangential force. Extent of 
increase of earth's rotation to make g ineffective. 

Wave-motion and the cether. Characteristics of all waves: 
resistance, persistence, over-shooting the mark. Transfer and 
conversion of energy in vave. Water waves and sound waves 
compared. Interference: water shadows and sound shadows. 

/Ether waves, artificial and natural. Electrons as charges 
of electricity. Surplus and deficit of electrons in discharge of 
Leyden jar; hence over-shooting the mark and train of oscilla- 
tions; analogy with weakening pendulum. Visualization of 
electromagnetic waves. The aether as a wave carrier; how its 
properties are deduced. 

Light. Velocity and how determined; inference from its 
equality to the ratio of static and electromagnetic units. The 
visible and invisible spectrum. Inference that actinic waves, 
light waves, heat waves, and electric waves are of the same 
nature. 

The eye and the ear. Their remarkable limitations. 

The phenomenon of aberration. Inference: a stationary 
aether, which is therefore a possible reference frame for all 
measurements. 

The Michelson-Morley experiment. Inference: aether not 
stationary but accompanies the earth in its travels. 

These two inferences obviously contradictory. Attempts to 
reconcile them: (i) by Fitzgerald and Lorentz, (2) by Einstein. 

The Fitzgerald- Lorentz contraction hypothesis. Professor 

Eddington's swimmer illustration, and the simple evaluation 

t 

Vv 2 
i 

Fitzgerald's suggestion of a physical contraction, to that extent, 
of the arm of the Michelson-Morley apparatus; the contra- 
dictory inferences thus reconciled. Theoretical confirmation 
by Lorentz. Why the contraction is impossible of detection. 
The contraction hypothesis quite plausible on the assumption 
of the electrical theory of matter. 



352 SCIENCE TEACHING 

The Lorentz transformation. Co-ordinate reference frames. 
Change of origin. Assume one frame fixed, and a second moving 
in the direction of the x axis. Then x = x r + vt, y = /, 
z = #', t = t\ The Lorentz transformation of these equations, 
by introducing the compensation factor into the first, and by 

modifying the fourth consequentially. Then x = t , &c. 



The consequential composition of velocities, not V = v : 
PI + P 2 



but V- 



(The whole of the preceding formed Einstein's jumping- 
off ground, and he now comes on the scene.) 

Einstein and Afterwards 

Einstein disliked the idea of a physical contraction, and he 
sought a more acceptable solution. He maintained that length 
was merely a relation between a particular object and a parti- 
cular observer, and he denied the independence of space and 
time. 

The Special Theory of Relativity 

Einstein's " special " theory is, at bottom, a new inter- 
pretation of the contraction (compensation) factor. The theory 
involves two principles: (i) All reference frames in relative 
uniform motion are on a par; (2) The velocity of light in vacuo 
is invariable, and is independent of the motion of the body 
emitting the light; and any observer measuring the velocity 
must always get the same result, irrespective of his own 
motion (if uniform and rectilinear) with regard to the body 
emitting the light. 

Each of the two principles seems to be true, although, as 
regards the second, there is no experiment to prove the invari- 
able concentricity of light-waves with respect to the observer. 



RELATIVITY 353 

But the two principles seem to clash. Einstein makes them 
consistent by adopting a new criterion of simultaneity. 

Criterion of Simultaneity. How determined. It follows that 
a metre scale moving relatively to a fixed scale reduces to 

^2 

i of itself, and tiiat a seconds-ticking clock in relative 
c 2 

motion seems to run slow, the time between successive seconds 
being increased by i / v i sec. Planes of simultaneity. 

No clear cut between past and future. (See the last section but 
one of this chapter.) 

It should be noted that the special theory provides an 
exact explanation of the effect of moving water on the velocity 
of light, as determined by Fizeau's experimental verification 
of Fresnel's hypothesis. 

The General Theory of Relativity 

i . Gravitation and acceleration : preliminary considerations. 
We say that a stone falls to the ground because of the existence 
of a force of gravitation, inherent in the earth's mass, which 
attracts the stone towards the earth's centre. But this is only 
part of the story. The stone's path is more accurately deter- 
mined by supposing the stone to be acted on simultaneously 
by two forces -a gravitational force of attraction towards the 
earth's centre, and a tangential (" centrifugal ") force arising 
from the earth's rotation. It is only because the rotation is 
comparatively slow that the hypothesis of attraction towards 
the earth's centre gives a fairly correct account of the fall of 
the stone. 

One of the first problems given to beginners in astronomy 
is to prove that the effect of the earth's rotation is to decrease 
the weight of a body at the equator by about 1/289 of the 
whole. If the earth rotated x/aSg (= 17) times as fast as it 
now does, the two forces would just balance, the " weight " 
of the body would be reduced to nil, and there would certainly 
be no tendency for the body to " fall " towards the centre of 



354 SCIENCE TEACHING 

the earth; and we should be driven to invent an entirel/ new 
hypothesis to explain the neutral motion of the body. If the 
earth rotated faster still, the motion of the body would be such 
that we should probably invent an hypothesis to the effect 
that the motion is due to a gravitational force of repulsion 
inherent in the earth. 

Obviously, then, it is easy to confuse gravitational attraction 
with acceleration arising from the earth's rotation. In fact, it is 
impossible to distinguish between the effects of gravitational 
attraction and the effects of acceleration of any kind whatever. 
Every aeroplane pilot knows this only too well. It is impossible 
to devise any instrument to show the direction of the vertical 
in an aeroplane, since the acceleration of the aeroplane produces, 
on any instrument, effects which are indistinguishable from 
those of gravity. 

Gravitational " fields of force " are therefore really illusions. 
The apparent " force " arises solely from acceleration, and we 
are bound to conclude that there is no other kind of gravi- 
tational force at all. 

The term " acceleration " is, of course, used in its wider 
sense. It may arise not only from a change in the amount of 
a velocity, but also from a change in the direction of the velocity. 
For instance, a motor-cyclist riding in a circle at a uniform 
speed of 60 miles an hour will be the subject of an acceleration 
towards the centre of the circle. He knows that the apparent 
force as produced is just as real in its effect as gravitation, 
and that he must, to save himself from falling as a result of 
its influence, incline to the vertical plane of his machine. 

It is of little use to proceed with the general theory of 
relativity until a boy sees clearly that gravitation is merely an 
effect of acceleration. An admirable handling of the subject 
may be found in a lecture by Professor Brodetsky, reproduced 
in the Mathematical Gazette for July, 1928. 

2. Artificial Gravitational Fields. How they may be created 
and destroyed. Gravitational mass and inertial mass; hypo- 
thesis of the electromagnetic origin of matter. Is gravitation 
identical with inertia? 



RELATIVITY 355 

3. Principle of Equivalence. It is impossible to distinguish 
between (i) a gravitational field of force, and (2) an artificial 
field of force resulting from accelerating a reference-frame. 
Illustration: an observer anchored in a room isolated in space, 
travelling with accelerated velocity in any direction; his infer- 
ences from the happeni igs in the room. 

4. The Four- dimensional Continuum. The union of space 
and time into " space-time ". The actual cause of gravitation 
had never been discovered, and Einstein asked himself if 
gravitation might not be merely some fundamental property of 
space-time. There is only one space-time, but this may be 
divided up into indefinitely numerous systems of space and 
time. We each have a space and time of our own, but we 
cannot divide space-time into space and time separately in 
the absolute sense. Every mode of division has a time-like 
aspect and a space-like aspect. Natural phenomena are not 
concerned with space and time separately. Our where and 
zvhen are always associated, even in the headings of our letters. 
Space-time considered as a four-dimensional continuum. The 
fourth dimension, t. The " flat-land " analogy may mislead, 
though the surface of a sphere is useful to illustrate a two- 
dimensional limited but unbounded space. Imaginary cine- 
matograph film of all the events of a man's life. (See the section 
on the Relativity of Simultaneity, infra.) 

5. Events and Intervals. Geometrical interpretation of the 
factor v/ i. (See the section on the Relativity of Simul- 
taneity.) The " interval " an absolute quantity, a unique dis- 
tance between " events ". The general interpretation of the 
equation ds 2 = dx 2 dy~ dz 2 + dt 2 . 

6. Curvature of the Continuum. Why the geometry of a 
gravitational field is non-Euclidean. " Curvature " of such a 
field indicates, primarily, deviation from Euclidean geometry. 
The curvature of the continuum cannot be visualized, but the 
curvature of light -rays crossing an accelerating lift is a useful 
analogy: this curvature is very slight because of the great velocity 
of light. " Curvature " is just a convenient term for a group 
of mathematical expressions analogous to those similar expres- 



356 SCIENCE TEACHING 

sions which in the geometry of surfaces do actually represent 
curvature. Sometimes we speak of a " warped " space-time 
or of a " distortion " of space-time, but neither term is any 
better than the term " curvature " for conveying to the mind 
any sort of picture of the thing concealed in the mathematical 
expressions. * 

7. " World lines " as (i) geodesies between two events in 
space-time; (2) tracks of particles in a gravitational field; (3) 
world-history. (" World "an ambiguous term.) 

8. Gravitation. The mathematics of the subject is much 
too difficult, and even advanced pupils must be content to 
understand the data with which Einstein began his analysis, 
and to understand, in a general way, the significance of his 
final result. Do not obscure main ideas by befogging them 
with symbols. The pupils may be told that it all works out 
to this that gravitation is some kind of curvature or distortion 
of space-time due to the presence of matter; and that this 
distortion is a necessary inference (of which no one questions 
the validity) from mathematical analysis, but that it cannot 
be visualized. Einstein's theory of gravitation is not a theory 
that enables us to picture a sort of working mathematical model, 
like Newton's model; it is a mathematical theory. Give some 
idea of the general equation of a two-dimensional surface, and 
of the possible extension to four-dimensional space-time. The 
actual gravitational " field " resulting from Einstein's analysis 
is, at bottom, extraordinarily like that enunciated by Newton. 
For all practical purposes, the inverse square law is produced 
by the relativity theory, but the form of the law is quite different; 
the new law is 



7 

Its appearance is altogether different from that of Newton's 
simple law, but, applied to particular cases, it gives almost 
identical results. Its great gain over the old law is that it 
accounts exactly for the few discrepancies that the old law 
could not be made to cover. 



RELATIVITY 357 

me only possible reason for preferring the old law to the 
new is that it is much simpler in form. There is no defence 
for such preference, unless it be sentiment. We are apt to put 
a child-like faith in clear mind-pictures, and to distrust mathe- 
matical analysis. But if the mathematical analysis is based on 
data which nobody questions, and if the logic of the analysis 
is irrefutable, how can final results be assailed, even though 
the mind cannot indulge its natural desire for picture-making? 
The real trouble with relativity is that few of us are good enough 
mathematicians to follow out the logic of Einstein's analysis, 
and we need not be ashamed to say so. 



Tests of the New Law of Gravitation 

The tests are three in number, and all are easily explained. 

1 . Rotation of orbit of Mercury. Confirmatory of new law. 

2. Deflection of light-rays in a gravitational field. Con- 
firmatory of new law. 

3. Displacement of spectrum lines towards the red. - 
Recent work confirmatory of new law. 

The pupils should know that the effect of these successful 
tests was so great that relativity has since received a world-wide 
acceptance. 

The Relativity of Simultaneity 

The following is a complete outline of a lecture-lesson on 
one aspect of relativity. It is complete enough for a well-trained 
Sixth Form boy to follow without help. 

Since all bodies are in a state of motion, the separate con- 
sideration of space and time must inevitably involve us in logical 
contradiction, and this is really the basic fact on which the whole 
fabric of relativity is constructed. But relativity does not mix 
up space and time into a sort of compound, the constituents of 
which lose their individuality and disappear. The four-dimen- 
sional space-time continuum is not suggestive of a new form 



358 SCIENCE TEACHING 

of fruit-cake, or anything else so absurd. The essence 6f the 
whole thing is that four variables are necessary to define the 
position of a given body at any given moment, three in space 
and one in time. All unconsciously we adopt the procedure 
of associating space and time every day of our lives when we 
begin a letter. We say where we ar^ writing and when. 

All this seems very simple. Then wherein lies the difficulty, 
if space and time seem so easily separable? The difficulty lies 
in the fact that space and time can not be separated from each 
other in any absolute way. The particular mode of separation 
depends on the particular observer, for, when two observers 
are in relative motion, events which appear to be simultaneous 
to one of them do not appear to be simultaneous to the other. 
It is useless to try to visualize the four- 
fold continuum, since it is merely an 
abstract conception, resulting from mathe- 
matical considerations. 




When we say that we "see", we mean 
that the news of more or less distant 
happenings is reaching us by means of 
light signals which travel with a constant 

velocity c. Hence, to an observer p, events will be simultaneous 
which are on the circumferential light-wave of which he is the 
centre, e.g. the events A, B, c, and D. (Fig. 7.) But while P has 
one conception of simultaneity, a second observer p', who moves 
out from P to P' while the wave is advancing from p, will have 
another. For it is a fundamental principle of relativity that 
the velocity of light is Constant to P' as well as to p, and events 
which are simultaneous to the former must therefore be on 
another circumferential wave-front DECF with himself as centre. 
Clearly, then, A, B, c, and D cannot be simultaneous for p'. 
If, as relativity demands, as experiments suggest, and as we 
feel bound to admit, the velocity of light with respect to 
observers in relative (unaccelerated) motion is invariably c for 
all, we have to abandon our old notion of absolute simultaneity. 
Einstein's criterion of simultaneity is this. He measures off 



RELATIVITY 359 

a length AB on a railway embankment, and places an observer, 
provided with two mirrors at 90, at the exact mid-point M. 
If light flashes emitted from A and B are perceived in the two 
mirrors by the observer at the same time, then the flashes 
must have been emitted d simultaneously. (Fig. 8.) 

He now considers a train moving with a constant velocity v, 
and we are to imagine that any event which takes place along 
the embankment also takes place at some particular point on 
the train. The criterion of simultaneity is to be applied with 
respect to the train in exactly the same way as with respect 
to the embankment. Einstein now asks if the lamp flashes 
which are simultaneous with respect to the embankment are 
also simultaneous with respect to the train. 

The events A and B correspond to positions A' and B' on 



Embankment 



A M B 

Fig. 8 

the train. Let M', the mid-point of A'B', be the position of the 
observer on the travelling train. When the flashes occur (as 
judged from the embankment), M' coincides with M, but is 
moving with the velocity v. 

But not only is the observer at M' hastening towards the 
beam of light coming from B, he is also riding on ahead of 
the beam coming from A. Hence he will see the beam of 
light emitted from B earlier than he w>ll see that emitted from 
A, not because the beam has changed its velocity but because 
it has a shorter distance to travel in order to meet him. He 
will thus conclude that the flash B took place earlier than the 
flash A. Hence events which are simultaneous with reference 
to the embankment are not simultaneous with respect to the 
train, and vice versa. Thus every co-ordinate reference system 
must have its own particular time; the idea of simultaneity 
is only a relative idea; " half-past one " has no absolute 
significance. 



360 SCIENCE TEACHING 

A general physical law can be so expressed that it is trans- 
formed into a law of the same form when, instead of the space- 
time variables x, y, z, t, of the original co-ordinate system (K), 
we introduce space-time variables #', y' , z' , t', of a new co- 
ordinate system (K a ). The relation between these two sets of 
magnitudes is given by the Lorentz transformation. 

We usually speak of " space " as three-dimensional, and we 
talk of length, breadth, and depth (or height). Are we justified 
in looking upon " time " as a fourth dimension, and of treating 
t as co-ordinate with x, y, and #? 

If a common house-fly is moving about a room, its position 
at any instant is determined by its distance from each of two 
adjacent walls and the floor, in other words by x, y, and z in 
that particular co-ordinate system. But the fly may move 
slowly or quickly, and to know all about the motion of the fly 
we must know the velocity with which it moves from point 
to point. But velocity is a term which involves the notion of 
time as well as space, and thus we must consider t as well as 
x,y, and#. Now all bodies are in motion; nothing is at absolute 
rest. If therefore we try to dissociate space and time, confusion 
will be inevitable. It is safer to speak of them together, and 
to speak of them as " space-time ". 

Relativity does not deal with four-dimensional " space ": 
it is not concerned with finding means for " ghosts " to get 
into and out of an hermetically sealed room! But it does deal 
with the four-dimensional continuum, space-time, which is a 
very different thing. 

The three co-ordinate x, y y and z planes are usually repre- 
sented at right angles to one another. The " up-and-down " 
direction is clearly at right angles to the " right-and-left " 
direction, and to the " backwards-and-forwards " direction; 
and so reciprocally with all three. These three directions seem 
to map out the whole of space as we know it, and it is clearly 
impossible to find a fourth direction at right angles to the 
other three. And relativity does not really demand this. Never- 
theless, in dealing with the four- dimensional continuum, in 
which one of the dimensions is time, it is perfectly legitimate, 



RELATIVITY 361 

within certain limits and under certain restrictions, to make 
time and space interchangeable. In this way we may easily 
show that events which are simultaneous in one system are not 
necessarily simultaneous in another. 

In visualizing any problem in which the relative motion of 
two systems alone is concerned, we usually, for convenience, 
choose the axis of x for the direction of motion, and take the 
axes of y and #, arbitrarily, at right angles thereto. But in 
dealing with such a problem, we can quite well do without 
one of the axes y or z, in which no relative motion in space 
is taking place, and so find room for the axis of time. It might 
be thought that we could do without both y and z y but from 
what follows it will be seen that the retention of one is neces- 
sary. 




Fig. 9 



We will confine all space movements to space of two dimen- 
sions, namely, to the vertical plane xy, x being the axis of 
relative space-motion of the two systems to be considered. 
The axis of x is represented as a horizontal, and the axis of y 
as a vertical, in the plane xy. The flow^of time t is represented 
by the discarded z axis, this t axis being, of course, at right 
angles to the xy plane, and, in the figure (fig. 9), running 
horizontally to the right. 

Any point p projected on the three planes xy y xt y yt> repre- 
sents an event, (i) at the abscissa distance oc, giving its position 
relative to o along the axis of x\ (2) at the distance OB, giving 
the time of its occurrence along the axis of /; and (3) giving 
its position F along the axis of y and above the horizontal 
plane xt. 



362 



SCIENCE TEACHING 



The two-dimensional plane xy is Euclidean, but the three- 
dimensional space-time xyt is not Euclidean; neither is the 
plane xt Euclidean. For the t ordinate represents time\ and 
in order that time, regarded as a fourth dimension, may be 
brought within a Euclidean system, it is necessary, as we shall 
see, to multiply it by the imaginary quantity v i. We 
must therefore determine how, geometrically, the three- 
dimensional xyt space-time may be converted into Euclidean 
form. 



y 




Fig. 10 



Suppose that, at the place and time defined by the position 
o (fig. io),.a luminous flash takes place. Then as time pro- 
gresses along the axis ^, the light emitted will proceed out- 
wardly from o as a spherically expanding shell. But as we have 
discarded one of the dimensions of space, and have therefore 
only two dimensions left, namely, a plane, only a plane section 
of this sphere can be spatially represented. This section is, 
of course, a circle, and as the space-plane moves along the t 
axis, the successive circles get larger and larger with the expand- 
ing light-shell. It thus comes about that, in our three-dimen- 
sional space-time figure, we have a light-cone with its apex 
at the origin and the axis of t for its own axis. We may pro- 



RELATIVITY 363 

visionally regard the xy space-plane as fixed relatively to our- 
selves, the progress of time being represented by that plane 
sliding uniformly along the t axis. 

From Einstein's criterion of simultaneity it follows that 
events on the circumference of, say, the circle PQ would be 
simultaneous; for if ne^v flashes of light were emitted at P 
and Q at the same instant of time, since the plane xy contains 
both the resulting light-waves they would clearly intercept at 
a point F on the t axis; symmetry shows that the conditions of 
simultaneity are fulfilled. 

Geometrically considered, since the plane xy moves freely 
parallel to itself, the successive circles may be supposed to 
represent planes of simultaneity for the xyt system to which 
they relate. We have reduced our space world to the relatively 
fixed two-dimensional plane xy, and every plane parallel to 
xy represents, in time, a plane of simultaneity for that system. 

So far, we have considered a relatively fixed reference 
system. Relatively, the observer does not move in space at 
all, not even along the axis of x. He and his reference system 
K simply move down the stream of time. It is as if he remained 
seated in his laboratory o, and the successive circles repre- 
sented successive seconds, successive days, or successive periods 
of some kind. The points on the circumference of a circle 
represent simultaneous events for the observer at the centre. 
There is movement in time only. 

But suppose there is movement in space also. At the 
instant the flash is emitted from o, let a point move with 
uniform velocity along the axis of x. Compared with the 
velocity c of light along the axis of t, me velocity of the point 
along the space axis x will, in all ordinary circumstances, be 
almost insignificant, but that does not affect the argument. 
The problem is: will the planes of simultaneity in the moving 
system i^ be the same as, or will they be different from, those 
in the relatively fixed system K? 

Let AB (fig. 10) be the horizontal diameter of the circle 
LAMB; OAB is thus the horizontal medial section of the cone. 
Through any chord DE parallel to AB, cut off a section DYE 

(E72) 2S 



364 



SCIENCE TEACHING 



of the cone, parallel to OAB. Obviously DYE is an hyperbola. 
Project this hyperbola to NGS in the plane OAB, and draw 
the tangent HK. This tangent is, of course, the diameter of 
another circle in a plane of simultaneity, viz. YHJK. 

Fig. ii is the horizontal oxt plane from fig. 10. The apex 
of the cone is shown as a right angli, for mathematical sim- 
plicity, but the general argument is unaffected. HK is the 
projection of the plane of simultaneity YHJK (fig. 10) upon the 
oxt plane, and is of course identical with the x axis which has 
moved down the stream of time t. Let o^ represent the path 
of the point in the moving system. Whilst it moves along the 





axis of t from o to G with the velocity of light, it moves in 
space along the axis of x from G to w. 

Fig. 12 represents the section of the light cone through the 
plane of simultaneity HK. In the fixed system, GH = GK = 
GY = Gj, so that the velocity of light in both directions along 
the x axis, and in both along the y axis (hitherto ignored) is 
the same, and the condition of constancy, c, is thus complied 
with. But if light from w in the moving system reaches H 
and K at the same time, the velocity in the one case is obviously 
greater than c, and in the other less; moreover, since WY t 
or wj x is less than GY or GJ, the velocity along WY X or wj l is 
less than c. Thus the condition of constancy is not complied 
with, and it therefore follows that planes of simultaneity for 
the moving system are not identical with those for the fixed 
system. 

We therefore have to adjust the co-ordinates for the moving 



RELATIVITY 



3 6 5 



systern in such a way that an observer in it cannot detect any 
variation in the normal velocity of light c. 

Fig. 13 is the greater part of fig. n repeated, with the 
addition of the hyperbola from fig. 10. 

The sides of the cone cut off equal intercepts from the 
tangent at G X , that is, G I /I I = G^. Hence the velocity of light 
is the same in both these directions of the moving system. 




Fig. 13 



Apparently, then, this new line x l may be regarded as the x 
axis of the moving system. It is a projection of the x^y plane, 
and it slides down o^ parallel to itself. It is a projection of 
a plane of simultaneity in the moving system. 

Thus we appear to have found a co-ordinate system x^ 
for a point moving relatively to the fixed xt system. There has 
been motion in time and in one direction in space. Using 
only one direction in space has enabled us to simplify the 
argument, which, however, may be considered sufficiently 
general. 

It is now necessary to see if, in the moving x^ system, 



3 66 SCIENCE TEACHING 

the principle of the constancy of the velocity of ngni is 
satisfied. 

From fig. 10 we see that all points on the hyperbola DYE 
are equidistant from the xt plane. Hence in fig, 13 the dis- 
tances from the points G and G l along the y axis to the conical 
surface are equal. Thus the condition that the velocity of 
light travelling at right angles to the direction of motion shall 
be constant, and the same for both systems, is satisfied if G 
occupies its position on the x axis of the fixed system, and G t 
its position on the x l axis of the moving system, at the same 
instant. 

But, at first sight, this equality does not seem to apply to 
the direction of motion itself. For, in fig. 13, KH is the projec- 
tion of a circle, and K I H I of an ellipse; and G^ or G^ is 
obviously longer than GH or GK. But since Gjiq = G 1 H 1 , the 
velocity seems to be equal in both directions, though greater 
than in the fixed system; and it might be thought that, for 
the moving system, the light wave-front due to the flash at 
o is elliptical. But this is impossible. 

The key to the difficulty is to be found in the fact that the 
xt plane (fig. 13) is not Euclidean. Physical lengths measured 
along a line involving time are not those measured on the 
paper. But if we multiply such lengths by V i they reduce 
to Euclidean lengths, and we then have the ordinary Euclidean 
geometry. In the case under consideration, GjHj or GjKj 
reduces to GH or GK, and our supposed ellipse in the moving 
system reduces to the circle in the fixed system. This will 
be demonstrated directfy. The principle of the constancy of 
the velocity of light thus holds. 

Thus, in the moving system, the apparently elliptical form 
of the expanding plane of simultaneity becomes truly circular 
when transformed by means of the multiplier x/ i. 

Some indications of the formal demonstrations may be 
given. 

We begin by adopting a simple geometrical device which 
may be spoken of as the V i transformation. 



RELATIVITY 



367 



Fig. 14 shows a length x compounded with a time t. The 
hypotenuse PR of the triangle PQR is obviously \/x 2 + t z . 




t 

Fig. 14 



Q 




Q 



t z is transformed 



But if we multiply t by \f i, then \/# a 
to N/# 2 t*. Fig. 15 
shows the geometrical 
construction for obtain- 
ing P'R' of this value, 
(p' is the intersection of 
a circle on R'Q' as dia- 
meter, and of a circle 
with centre Q' and radius 
x.)* Note that the general 
direction of RP is only 
very slightly modified 
when transformed to 



We proceed to in- 
dicate the steps of the 
main demonstration. 

In fig. 1 6, the points 
o, GJ, HJ, KJ are as in fig. 
13. Through G l draw 
ABC at right angles to ot. 
With centre B and radius 
BA or BC draw the semicircle COA, and draw the perpendicular 




* It might be argued that the figure suggests V t* x* rather than ^ ' x* ^l 1 , and, 
in point of fact, t actually is usually very much greater than x. But the important 
thing here is difference of sign. By making t negative, we can conveniently keep x, 
y, and z positive. 



368 SCIENCE TEACHING 

GjF to meet it. This ordinate GjF is obviously equal 10 the 
semi-minor diameter of the ellipse (cf. WY X in fig. 12) which 
has been swung round on G l fiom the vertical into the hori- 
zontal plane. 

To the triangle OEG I apply the \/ i construction of fig. 
15, so that OM corresponds to R'P' in that figure; OM is thus 
the real length of OG X . But since U^OK^ is a right-angled tri- 
angle, and G! is the mid-point of the hypotenuse, Gjjq = 
GjO = G^. Hence OM is the real length of Gjiq and G^. 

Again, in the triangles OEM and PEG^ BO = BF, BM = BG I , 
and the angles OMB and FG X B are right angles. Hence the 
triangles are congruent, and FG X = OM, the semi-minor dia- 
meter of the ellipse. This semi-minor diameter is therefore 
equal to the transformed and real lengths of the semi-major 
diameters G^ and G^. In other words, the apparent ellipse 
is a circle, and the velocity of light is therefore constant in 
all directions. Q. E. D. 

The apparently elliptical form becomes a circle when the 
*/ i transformation is carried out. The circle is necessary 
because we have to obtain conditions complying with the 
principle of the constancy of the velocity of light, but the circle 
is obtainable only by treating t differently from x y y, and z. 
Thus we say that the space-time represented in our figures 
is not strictly Euclidean. 

Since a plane of simultaneity in the moving x l system (KJ) 
is not parallel to, but inclined to, a plane of simultaneity in 
the x system (K), we see that events which are simultaneous 
in one system are not simultaneous when considered as happen- 
ing in a system in motion relatively to it. 

The measurement disclosing the shortening of a body in a 
system K^ must be made, not in the plane of simultaneity K t> 
but in the plane of simultaneity K, and vice versa. The shorten- 
ing is in the measurement of the body in motion, made from 
the body supposed to be at rest; it is manifest only when the 
movement* of one body is made from the standpoint of another 
body moving relatively to it. Of course it is a reciprocal 



RELATIVITY 369 

phenomenon. From the point of view of the physicist chained 
to his own system, which he therefore considers at rest, and 
making his observations from that system, his measurements 
of bodies moving relatively to him reveal a shortening which 
to him seems real. 

From some point in the intersecting line of two planes of 
simultaneity in two relatively moving systems, let two lines 
be drawn, one in each plane. The other ends of the lines 
will, in general, occupy different positions in time. Thus 
while we can compare one end of each of the two lines at some 
given instant, we cannot compare the other ends at the same 
instant. The two comparisons are not simultaneous events. 
Instantaneous comparisons in relatively moving systems are 
impossible because of our dependence on light signals, and thus 
the relatively moving thing always appears to be shortened. 

This shortening is not, according to relativity, a physical 
shortening. It is an apparent shortening for an observer chained 
to some other system in relative motion. 

It is important for pupils to grasp the principle that two 
observers s and s x in their respective systems K and K x are 
affected in precisely the same way. The arguments through- 
out are reciprocal. 

Fig. 17 is a slight modification of fig. 13. 

ox and ot are the space and time directions, respectively, 
of the observer s; and o^ and o^ of s x . OL and 01^ are the 
light lines representing the section of the light-cone made by 
the xt plane. Let ow and OG be equal and represent unit dis- 
tances in space and time, respectively, in the system of s. 
In the system of s x , GWj = OGj, where the units are obviously 
a little greater, depending on the observer's own reckoning. 
OWjKjG! is evidently a rhombus. 

S will consider his own space-time reference system to con- 
sist of a framework of squares, but will consider the reference 
system of s x to consist of a framework of rhombuses. On the 
other hand, Sj will consider his own reference system to con- 
sist of squares, and that of s to consist of rhombuses. For 
each the other's framework of squares will be distorted. 



SCIENCE TEACHING 

" Shape " is something which each himself puts into nature. 
For each the partitions of his own framework are unit distance 
apart in space and time, according to his own reckoning. 
But although the two disagree about lengths and durations, 
they do agree about the constancy of the velocity of light. 
(Figs. 18, 19.) 

The farther K t is taken along OL, the more elongated the 
rhombus, and the larger the unit divisions oWj^ and OG V The 




Fig. 17 



line ot t then lies nearer and nearer the light line OL. Such an 
elongated framework would seem by s to be made by s l if the 
latter were travelling at a very great velocity. In the limit, 
when the velocity reaches that of light, both the space unit 
and the time unit become infinite; and s will conclude that 
the length of every object in s/s system has been reduced to 
zero, and that all events in s^s system take place " in no time ". 
This is really an exaggerated way of saying that the velocity 
of light is a limiting velocity. 



RELATIVITY 371 

We may conclude with an illustration, but the pupils must 
remember that all analogies are likely to mislead. 

Imagine a continuous film record of the whole of a man's 
life to be taken. (In practice, of course, cinematographic " con- 
tinuity " is impossible, for the pictures on a film are not pictures 
of events at consecutive 1 point-instants. Gaps are inevitable, 
for every picture takes an appreciable time for the making. 
Ordinarily only about sixteen pictures a second are taken, 
and clearly a great deal may happen that the film cannot 
record.) Imagine the film to take in a background of sufficient 
expanse to include every movement, no matter how exten- 
sive, of the man during the whole of his life. Now let the 



W 



O G 




Fig. 1 8 



Fig. 19 



individual pictures be separated and piled in a block (con- 
ceivable, though not imaginable, because the number is infinite). 
We have a three-dimensional (xyt) space-time record of the 
man's life. Each separate section of the film is, for the man, 
a record of simultaneous events at a particular moment. If 
the film were reproduced on a screen, we could lengthen or 
shorten the time component of the f space-time continuum 
merely by varying the speed of turning the machine. Could 
we but see the whole of the successive pictures in the three- 
dimensional block simultaneously, that is, all at the same 
instant, as completely and fully as we can see an ordinary 
object at rest, then we should have some idea of how a man 
might be represented in four-dimensional space-time. 

Now let the whole block of superimposed films be fused 
into a single block, the separate laminae, as such* all disappear- 
ing. And let the block be cut into laminae again, but by parallel 



372 SCIENCE TEACHING 

planes in a direction oblique to the former. The new' films 
may be regarded as representing the background of a second 
person's life (the distortion of the original pictures will, for 
this purpose, be immaterial), and each film will again be a 
record of simultaneous events for a particular instant. But 
the new films will intersect the old.* Hence what was simul- 
taneity for the first person will not necessarily be simultaneity 
for the second, except where the planes intersect. 

Unsolved Relativity Problems 

Intelligent boys may profitably be given some idea of the 
problems engaging relativists, astronomers, and others at the 
present time: 

1. The hypothesis of the electromagnetic origin of matter. 

2. Gravitation and electricity: attempts at unification. 

3. Is there an aether? Relativity asserts that the four- 
dimensional continuum has a structure. Hence it cannot be 
the mere void of empty space, though relativists refuse to 
identify it with a Maxwell aether, subject to the laws of dynamics. 
We may perhaps consider the " universe " to refer to the con- 
tinuum which includes all things visible, i.e. the stellar universe, 
the matter-containing universe, conceivably wholly within a 
limitless void. 

4. The size of the stellar universe. Light takes a million 
light-years to reach us from the Andromeda nebula, and it is 
calculated that the universe may extend 20,000 to 100,000 
times as far as this, i.e*. its radius is about io 23 miles, and its 
circumference about 6 x io 23 miles. If radiated light remains 
within this universe, and travels round and round (as is thought 
to be the case), it completes the circuit in 6 X io 23 /6 X io 12 
years, i.e. io 11 years, i.e. it goes round io times every billion 
years, travelling at the rate of 186,000 miles a second. If we 
could visualize this line, the curvature would seem so slight 
that even any billion miles of it would look absolutely straight. 

It is an impressive fact that light travels round the earth 



RELATIVITY 373 

in > 01 a second, and yet seems to require a hundred thousand 
million years to travel round the universe. 

The pupils should know something of the method adopted 
or calculating the volume of space-time by measuring the 
density of the distribution of matter in space. 

Try to give the boys s'ome idea of the value of the evidence 
on which all these estimates are made, and what a large number 
of hypotheses, some of them highly speculative, are involved. 
Insist that we may be a very long way from the actual facts. 
Urge caution. 

Another Warning 

The astronomical model of the atom lends itself all too 
readily to picture-making, with the consequence that it in- 
spires us with an almost royal confidence in its reality, a 
confidence which, though natural, is quite unwarranted. But 
Einstein's warped space- time defies all attempts to picture it, 
a fact which makes many people sceptical of the validity of 
the whole theory of Relativity. The scepticism in the second 
case is, however, as unwarranted as the over-confidence in 
the first. See Chap. XXXVI, 4. 



CHAPTER XXXIII 

The very Great and the very Small 



When attempting to help a boy to form a clearer conception 
of the significance of very large numbers, say those concerning 
stellar distances or atomic magnitudes, it is essential for the 
teacher to eliminate from the problem every kind of avoidable 
complexity. To form a conception of a great number is quite 
difficult enough in itself, and to a boy the difficulty may prove 
insuperable. On one occasion I heard a teacher attacking our 
old friend the " light-year ", in favour of its aew rival the 
" parsec ", simply on the ground that the latter made astro- 



374 SCIENCE TEACHING 

nomers' computations easier. Now the light-year is a perfectly 
well understood thing. In mechanics we often define distance 
as the product of velocity and time (s = vf) > as every child 
knows; and we apply this self-same principle to the distance 
known as a light-year, the new unit being determined by the 
product of the velocity of light (miles per second) and the 
number of seconds in a year. But the parsec is the distance 
corresponding to the parallax of i", and a simple calculation 
shows that it is 3-26 times as long as the light-year; and this 
trigonometrical method of determining star distances compels 
the learner to think in terms of the semi-major axis of the 
earth's orbit. The complexity is entirely unnecessary in school 
work; it tends to obscure the main thing the boy is supposed 
to be thinking about. 

Simple arithmetic tells the learner who knows that the 
velocity of light is 186,000 miles a second, that the length of 
the light-year is, approximately, 

(186,000 X 60 X 60 X 24 X 365) miles, i.e. 6 X io 12 miles, 

or 6 billion miles. Thus, when the learner is told that a Cen- 
tauri is 4 light-years distant, he knows that this means 24 billion 
miles; and that the 1,000,000 light-years representing the 
probable distance of the remoter nebulae is a distance of 
6 X io 18 (six trillion) miles. Or, he may be told that the mass 
of the H atom is 1*66 x io~ 24 grams, when he sees at once 
that io 24 H atoms together must weight if grams. 

But are these vast numbers anything more than mere words 
to the boy? What do^s a quadrillion signify to him? or even 
a trillion or a billion? or even a million? Is it of any use to 
try to make the boy realize the significance of such numbers? 
or just to leave them as mere words? or not to mention them 
at all and merely to give some such illustration as Kelvin's 
earth-sized sphere full of cricket-balls? 

I have tried the experiment of giving to boys such illus- 
trations as these: (i) the number of molecules in i c. c. of 
gas is about, 200 trillions (2 X io 20 ), a number equal to the 
number of grains of fine sand, 70,000 to the cubic inch, in a 



THE VERY GREAT AND THE VERY SMALL 375 

layer i foot deep, covering the whole surface of England and 
Wales; (2) the number of molecules in a single drop of water 
is about 1700 trillions (1-7 X io 21 ), a number just about equal 
to the number of drops of water in a layer 7^ inches deep 
completely covering a sphere the size of the earth. But I 
have always found that auch illustrations merely give rise to 
vague wonderment. The pupil himself makes no personal 
effort to realize the magnitude of the numbers; and this is 
fatal. 

Such an effort is indispensable. The best plan, perhaps, 
is to make the pupil first consider carefully the magnitude of 
a million, then of a billion, a trillion, a quadrillion, successively 
(io 6 , io 12 , io 18 , io 24 ). For instance, an ordinary watch ticks 
5 times a second or 1000 times in about 3 minutes, or a million 
times in about 2 days and 2 nights. Let this fact be assimilated 
as a basic fact, first. Now let the boy think about a billion. 
Evidently, a watch would take (for the present purpose, all 
the underlying assumptions may be accepted) about 6000 
years to tick a billion times (2 days X io 6 ), so that if a watch 
had started to tick at the time King Solomon was building the 
Jewish temple, it would not yet have ticked half & billion times? 
Now proceed to a trillion, and then to a quadrillion. Evidently 
the watch would take 6000 million years to tick a trillion times, 
and 6000 billion years to tick a quadrillion times. An approach 
of this kind to the subject does not take long, and a boy fond 
of arithmetic may be encouraged to invent illustrations of his 
own. It is worth while. It is worth one's own while, if the 
attempt has never been made before. It is, indeed, hard to 
realize the significance of the statement that light-waves tap 
the retina of the eye billions of times a second. Yet how are 
we to escape accepting this frequency if we accept the measured 
velocity of light and the measured length of light-waves? 
Impress upon the boys the fact that the inference is inescap- 
able. 

The description of the manufacture of such a thing as a 
diffraction grating with lines ruled 20,000 to the inch, or of 
Dr. J. W. Beams' mechanical production of light flashes of 



376 SCIENCE TEACHING 

only io~~ 7 second duration, serve to impress pupils wifh the 
sense of reality of small things. 

Professor Haas, accepting De Sitter's suggestion as to the 
size of the universe, and the average density of matter in the 
universe, estimates the mass of the universe to be io 54 grams, 
and, since there are about io 24 electrons in a gram, there 
must be about io 78 electrons in the universe. Haas suggests 
(The New Physics, pp. 152-3) that in thought this number 
may quickly be arrived at by means of an exercise of this 
sort: 

" It is well known that bacteria are peculiar in that they 
propagate by a process of division of the individuals. From 
one bacterium in the course of an hour, there result two 
bacteria by this splitting-up process, and after an interval of 
two hours there are four, and so on. Let us suppose we have 
a single bacterium in a glass of water, and that it has the thick- 
ness of about a thousandth of a millimetre and twice this length. 
It would thus be approximately a billionth part of a gram 
in weight, and made up from roughly a billion electrons. We 
shall further assume that in some way or other, sufficient 
nourishment can be supplied to ensure that reproduction is 
not adversely affected by lack of food. In such circumstances 
there would be present some 16 millions of bacteria after one 
day, i.e. 24 hours; at the end of the second day there would 
be 300 billions, and after 3 days about 500 trillions, which 
would already correspond to a weight of thousands of tons. 
In the course of the sixth day, the mass of the bacteria pro- 
duced would exceed the mass of the earth; in the course of 
the seventh day, the rftass of the sun; in the course of the 
tenth day, the weight of all the bacteria would attain to the 
total weight of the universe; and finally in the course of the 
eleventh day the number of all the bacteria that would have 
developed from the original one would be as large as the total 
number of electrons in the universe/'* 

It does not pay to spend much school time over this sort of 

* The figures Jo not quite agree with recognized British estimates. See pp. 
377-8. 



THE VERY GREAT AND THE VERY SMALL 377 

thing? but it is useful to teach the boys some method of 
apprehending great numbers intelligently, if only in order 
that they may grasp the tremendous significance of such 
numbers. 

Boys must understand that both stellar magnitudes and 
atomic magnitudes are, for the most part, calculated values 
and not directly measured values, and that the calculations 
are, in the main, based on inferential evidence, the inferences 
being drawn partly from known facts, partly from hypotheses. 
But converging evidence of different kinds justifies a feeling 
of confidence in the probability of the truth of the estimate. 
So much so is this the case, that the natural repugnance of 
the mind to accept statements which seem to be so contra- 
dictory of everyday experience, and therefore to " common 
sense ", is overcome. Still, the nature of the evidence avail- 
able must be borne in mind. So must the amazing nature of 
the results! 

It is a curious and interesting fact that certain chemists 
of the old school demur to accepting the electron theory, 
solely on the ground of the utter insignificance of the size 
and mass of the electron. And yet they readily accept the 
atom and its estimated size and mass. Really, there is no 
appreciable difference in the order of the magnitudes. Approxi- 
mately, it is just a question of io 24 and io 27 . 

In their Biology, Professors Haldane and Huxley give an 
interesting table of comparative sizes. Here are a few of them 
(the numbers refer to grams): 



Minm. wt. of universe 1-8 X io 57 
Sun . . . . . . 2 X io 33 

Earth 6 x io 27 

Average man . . io 5 

Mouse. . . . . . io 2 

Bee 10 



Ant * io" 

Water flea . . . . io" 

Tubercle bacillus . . io~ 

Gene (hereditary factor) io~ 

Water molecule . . . . 10" 

Electron . . . . io~ 



A Sixth Form boy may usefully memorize a few of such well- 
known magnitudes as the following, now generally regarded 
as having been calculated with acceptable accuracy: 



378 



SCIENCE TEACHING 



Mass of an electron 

Mass of H atom 

Radius of K orbit of H 

Balmer frequency constant, B 

Rydberg constant (wave- number), R 

Mols. in i c. c. of gas (N.T.P.) 

Light year 

Distance of remoter nebulae 

Radius of stellar universe 



0-9 X io~ 27 gm. 

1-66 X io~ 24 gm. 

5-27 X io~ 9 cm. 

(3-29 X io 15 ) per second 

109677-69 

2-8 X io 19 

(ot X io 12 ) miles 

i o 6 light years = (6 X i o 18 ) miles 

io 23 miles 



As for microscopic magnifications, boys should be taught to 
calculate these for themselves. 



CHAPTER XXXIV 

The History of Science 

Why the History of Science should be Taught 

Whether or not science is taught on an historical basis, 
definite instruction in the history of science, outside formal 
experimental and theoretical lessons, should be included in 
every science course. The more serious work should be done 
in Form VI, by which time the boys will have amassed a 
multitude of facts, and these the history lessons will serve the 
purpose of placing in an appropriate setting. 

If the science teacher is lucky enough to have a history 
colleague whose sympathies are primarily on the side of the 
creative genius, whether of science or art or literature or music, 
his task will be comparatively easy. But there are still history 
teachers and history books that give prominence to such 
stories as those of a ruffianly baronage, of court intrigues, and 
of military and political adventurers. The stupendous events 
that have really made the world what it is are almost unknown 
to many of our children. The names of the great pioneers and 
discoverers, me things they have done, of what races they were, 



THE HISTORY OF SCIENCE 379 

and how though separated by nationality each has built on the 
work of the rest: these are the things that history should teach. 
The year 1848 is mentioned in the history books as memorable 
for political " revolutions ": how few of them mention that 
that was the year when Pasteur discovered the properties of 
asymmetrical crystals, a discovery which led to the birth of 
bacteriology, and thus to modern surgery, modern medicine, 
and other discoveries unrolling in almost endless series? Our 
historical perspective has been all wrong. There are still 
people who would place Maryborough and Napoleon, Richelieu 
and Palmerston, in the same rank as such mighty creative 
geniuses as Newton and Shakespeare, Rembrandt and Beet- 
hoven. 

But the history of science is a very big thing, too big for 
detailed treatment in the small amount of time available at 
school. The little that can be done should be supplemented 
by a good deal of reading. We throw out a few suggestions for 
lessons. 



General Lessons on Earlier Science 

1. The Egyptians and Babylonians: nations with a practical 
genius rather than an intellectual. Compare with ourselves. 

2. The Greeks: Hellenic genius essentially intellectual. 
Thales, Pythagoras, Plato, Aristotle. 

3. Alexandria: succeeded Athens as the centre of Greek 
culture. Euclid, Archimedes, Apollonius. 

4. Rome: not intellectual; all-round excellence in things 
technical. Again compare with ourselves. Roman engineering 
and architecture. Contempt for purely scientific studies: the 
Romans exploited everything in the interest of immediate 
application. 

5. Me diceval Science: Roger Bacon. Hostility of the Church. 
Why the Churches have always disliked science. The mariner's 
compass, printing, gunpowder: the far-reaching changes 
revolutions in the true sense that followed on the.e inventions. 

6. Bacon: scientific method worked out. 

(K72) 26 



380 SCIENCE TEACHING 

7. From Alchemy to Chemistry: Paracelsus. Phlogiston. 

8. Ancient Astronomy: Egyptian, Babylonian, Greek; Pto- 
lemy. 

9. Pioneers of Modern Astronomy: Copernicus, Tycho 
Brahe, Kepler, Galileo; then Newton, Sir W. Herschel, La 
Place. 



Lessons on the History of Particular Subjects 

1-6. Chemistry: the primitive metallurgists and their won- 
derful work; the early manufacture of glass, soap, dyes, pig- 
ments, medicines, oils, perfumes, and the great range of 
practical knowledge of the very early chemists; the paralysing 
effect of alchemy on chemistry for many centuries. The age 
of chemical discovery: Priestley and oxygen; Scheele and 
analysis; Cavendish and the atmosphere; Lavoisier and the 
balance and the overthrow of the phlogiston theory. Glimpses 
at the work of Black, Dalton, Avogadro, Davy, and perhaps of 
Berzelius, Liebig, Dumas, Mendeleeff, and later chemists. 

So with other subjects: dwell on the big leaps forward as 
the result of new discoveries. Let discovery and invention, as 
well as pure science, play a part in the lessons; for instance: 

7. The History of Textiles, especially as associated with the 
names of Hargr eaves, Arkwright, Crompton, Kay, Cartwright. 

8. The History of Steam: Watt, Fulton, Stephenson, 
Parsons. 

9. Iron and Steel: Siemens, Bessemer, Carnegie. 

10. Evolution: Darwin, Wallace, Huxley, Keith. 

11. Telegraphy: Morse, Wheatstone, Kelvin, Marconi. 

12. Gravitation: Newton, Einstein. 



The Personalities of the Great Workers 

From the multitude of the world's past and present distin- 
guished workers, the science teacher should select a few of 
the very greatest, and dwell upon their lives not only as great 



THE HISTORY OF SCIENCE 381 

men^)f science but as great personalities. Not the least interest- 
ing side of the characters of most great men of science is their 
remarkable devotion to their work and their self-sacrifice. 
In the very forefront we should place perhaps the greatest 
man of science the world has yet produced, our own Newton; 
and then perhaps Faradfy that remarkable physicist who knew 
nothing of mathematics. Then perhaps Darwin. And then 
perhaps Pasteur. Opinions will differ about the choice of these 
four. That does not matter. Let the teacher choose the few 
(there is only time for a few) he loves best and has made his 
own familiar friends, and can talk about intimately. Let him 
make these live their lives over again, so that the boys may 
get to know them. 

As for the multitude, time will not permit of much more 
than the association of each worker's name with his work. 
The name of La Place will always call up the idea of the nebular 
hypothesis; Koch, bacteriological investigation; Harvey, the 
circulation of the blood; Franklin, the identification of lightning, 
and electricity. The man himself we may not have time to 
say much about, but at least we may let his work enshrine his 
name. 

We British people may well be proud of our share in 
scientific discovery. To name only a few workers: Priestley, 
Rumford, Black, Davy, Cavendish, Perkins, Dewar, Ramsay, 
Crookes, Gilbert, Boyle, Young, Davy, Faraday, Tyndall, 
Maxwell, Kelvin, Lodge, Rutherford, J. J. Thomson, Darwin, 
Wallace, Huxley, Lyell, and many a dozen more. And we 
have to our credit the fact that we have discovered a third of 
the 92 elements. 

But science has no regard for national boundaries, and 
do not let boys tend to underrate the work of the scores of 
distinguished foreigners. France has given the world Cuvier 
and Lamarck, Gay-Lussac, Lavoisier, Dumas, Ampere, Arago, 
La Place, Becquerel, Moissan, and Pasteur. Germany: Guericke, 
Humboldt, Bunsen, Kirchhoff, Helmholtz, Virchow, Liebig, 
Weismann, and Koch. America: Franklin, Dana, Westing- 
house, Edison, Bell, Holland, the Wrights, Tesla, and Michel- 



382 SCIENCE TEACHING 

son. Italy: 'Galvani, Volta, Avogadro, Marconi. Sweden: 
Scheele, Arrhenius, Berzelius, Linnaeus, Nobel. Holland: 
van't Hoff, Huyghens, and Lorentz. Denmark: Oersted. 
Austria: Mendel. Poland: Madame Curie. Russia: Men- 
deleeff. Every boy should have some idea of the work that 
makes such names stand out so prominently, and if he has time 
to read up the lives of some of the workers, so much the 
better. 

Above all, make the history alive. Let it be something 
more than bare bones. Take Archimedes back to his bath, 
and let the boys picture his glee when the overflowing water 
gave him the clue to finding relative densities. Picture Avo- 
gadro sitting down to solve his puzzle how to give a rational 
explanation of the simple law of Gay-Lussac. Try to realize 
Newton's satisfaction when he discovered that the moon was 
merely the twin of a falling stone. 

Teach the boys how to prepare helpful history charts. 
For instance, they might take the great names and the great 
events in science and chart them to a time-line, and so represent 
graphically the centuries of plenty and the centuries of famine. 

Dates 

Every boy knows the dates of Hastings and Waterloo, 
but why are these regarded as landmarks more worthy of 
inclusion in a history course than are the great discoveries of 
science? 

Here are a few date$ that every student of science should 
remember: 



1300 Spectacles. 

1450 Printing. 

1530 Spinning-wheel. 

1687 The Principia. 

1705 Newcomen's engine. 

1764 Watt's engine. 

1767 Spinning-Jenny. 

1796 Vaccination. 



1836 Telegraph. 

1839 Photography. 

1846 Anaesthesia. 

1858 Atlantic cable. 

1859 Origin of Species . 

1860 Spectroscope . 
1868 Antiseptic surgery. 
1876 Telephone. 



THE HISTORY OF SCIENCE 383 

These are also worth committing to memory: 

Plato . . 427-347 B.C. 

Aristotle . . 384-322 B.C. 

Archimedes . . 287-212 B.C. 

Roger Bacon. . 1214-1294 A.D. 

Francis Bacon 1561-1^26 A.D. 



Galileo 1564-1642 

Newton 1642-1727 

Faraday 1791-1867 

Darwin 1809-1882 

Pasteur 1822-1895] 



The principal object of memorizing a few dates is the fixing 
of great landmarks. There is little point in memorizing a large 
number. 



CHAPTER XXXV 

Research: its Significance and 
Importance 

Sixth Form boys are invariably interested in learning some- 
thing about the patience and toil of those who were at last 
rewarded by making the discovery of what they set out to 
seek. The path of the research-worker is arduous indeed. 
Sometimes, it is true, a great discovery has been hit upon by 
accident, but, as a rule, scientific discovery has been the result of 
persistent effort, often extending over a long period. Edison's 
methodical world-search for a suitable material for lamp fila- 
ments is proverbial for its persistency. For a hundred years, a 
search for a cure for diabetes had be$n prosecuted, and the 
discovery of insulin was the eventual reward. Scores of 
specialists all over the world are now searching for the cause 
of cancer, and are making use of the work of chemists, bio- 
chemists, bacteriologists, and biologists, but so far they have 
not succeeded, despite their years of unremitting toil. The 
cause once found, a cure will probably follow. 

If all the boys of our secondary schools can be convinced 
of the value of scientific research, they will probably spread the 
light, and the nation will cease to tolerate the common and 



384 SCIENCE TEACHING 

long-standing Dependence of research upon chance opportunities 
and limited resources. Could the Government be induced to 
pay 10,000 a year to each of fifty of the leading consultants 
of Harley Street (a salary perhaps large enough to induce them 
to give up their present work of patching up chronic invalids), 
in order that they might undertake systematic research into 
the causes of the common ailments that afflict humanity, such 
ailments would probably be stamped out within a generation. 
But this is a most unlikely thing to happen. The practical 
thing to do in schools is to tell the boys what research workers 
have done, what they are doing, and about some of the things 
that still remain to be done. 

Such books as Newton's Opticks, Faraday's Researches, and 
Darwin's Earthworms, should be read by all Sixth Form boys, 
for they show exactly how the workers set about their work and 
how they made their discoveries. They afford a real insight 
into the spirit of research, and not a few of our leading men of 
science acknowledge that it was books of this type that first 
stimulated them to research on their own account. 

The boys should be told something of the work now being 
done by various government and university departments of 
research; for instance: 

1. The National Physical Laboratory, its physical, engineer- 
ing, chemical, aerodynamical, and other departments. 

2. The Government Department of Scientific and Industrial 
Research: researches into chemistry, building, foods, forest 
products, fuel, water pollution, radio. 

3. Rothamsted Experimental Station at Harpenden; its 
work on plant nutrition and diseases. 

4. The Cambridge Plant-breeding Institute: Sir Rowland 
Biffin's work on wheat. 

Then there are researches into insect-pest control; the 
Hayling Island mosquito station and Dr. Tillyard's work in 
New Zealand; research into fisheries; the work of the Safety- 
in-Mines Research Board; the scheme for Empire research; 
the work of research chemists in America and Germany, espe- 



RESEARCH 385 

cialiy in synthetic organic chemistry and the production of 
drugs, dyes, perfumes, flavours, &c.; the work of the Medical 
Research Council; the research of individual workers, e.g. 
that of Mr. Baird on television. Again: there is a notable in- 
crease of international scientific relations, and something should 
be known about recent^congr esses on geology and geophysics, 
on genetics, and on zoology. 

It is desirable to get boys interested in what scientific 
workers are doing all over the world, in their difficulties, their 
failures, their successes, their rewards. Arrange visits to places 
where such work is in progress. Visitors to research institutions 
are often given a cordial welcome. 

Reports on the work of research committees and research 
workers should be made available. They are often too long and 
too technical for boys to read, but an occasional short lesson 
or lecture may often be given, and with profit. Consider, for 
instance, the last annual report of the Research Board for 
Safety-in-Mines. Here is a short summary suitable for a 
lesson: 

1. Falls of ground, and types of props to be used. 

2. Wire ropes for winding corrosion of the end of the rope where 
it enters the capping; bending stresses in the rope where it passes 
over the pulley; injury of ropes by constant alteration of stress. 

3. Lighting efficiency of mine lamps; electric and flame lamps. 

4. Coal-dust and fire-damp explosions. 

5. Mining explosives. 

6. Electrical appliances for use in underground work. 

7. Mine rescue apparatus. 

In a mining district, a lesson of this kind would be in- 
valuable. 

When a boy leaves school, he should have been so taught 
and be so informed that he is able to take an intelligent interest 
in all scientific, technical, and industrial developments. He 
should be able to turn up technical reports, and obtain at 
least an intelligent general grdsp of their contents. He should 
be able to discuss in a council chamber fhe pros and cons of 
proposed new applications to industrial processes. In short, 



386 SCIENCE TEACHING 

the former secondary school boy should be the dissemiAator 
of new knowledge and the intelligent adviser of the com- 
munity. 

Boys should also be encouraged to take an interest in 
subjects which are not strictly scientific but which require an 
intelligent garnering of facts, some of them technical, for their 
complete understanding. The metric system of weights and 
measures, decimal coinage, the advantages of linking up the 
natural history museum with Kew Gardens and the Zoological 
Gardens, and the reform of the calendar, are such subjects. 
They may sometimes be profitably made subjects of debate in 
school science societies. 



CHAPTER XXXVI 

The Philosophic Foundations of Science 

First Notions of Philosophy 

We may regard philosophy as a subject which examines 
critically the fundamental principles of all departments of 
systematic thought, including metaphysics, ethics, aesthetics, 
mathematics, and science. At least metaphysics will be ruled 
out as a possible subject for treatment in school; it requires 
a fuller and a more mature mind than that of a school boy. 
Ethics may possibly be touched upon in connexion with 
religious and moral training, and aesthetics in the teaching of 
art. In mathematics, a Sixth Form boy ought to know, amongst 
other things, that his school geometry is based upon a parti- 
cular series of axioms adopted by Euclid; that other series of 
axioms, giving rise to entirely different schemes of geometry, 
might have been adopted, instead; and that, generally, the 
foundations of mathematics consist of shifting sand rather 
than solid rock,. As regards science, the Sixth Form boy ought 
to be taught that the time has come for him to try to examine, 



PHILOSOPHIC FOUNDATIONS OF SCIENCE 387 

undSr the philosopher's microscope, the variouk assumptions 
he has been allowed to make during his scientific studies; 
that he must now learn to examine the nature of scientific 
evidence, hypotheses, induction, and laws; to examine the 
foundations of his mechanics, physics, chemistry, and biology. 
In short, he must try*to learn to do as all philosophers do, 
viz. test the validity of the various assumptions made by 
science, and examine the principles of scientific method. Such 
work he cannot carry far: it is too difficult; but he should 
carry it as far as he can. 

Thoughtful boys are frankly puzzled at the inability of such 
a famous scholar as Aristotle to follow out his own unexception- 
able principles, and at his tendency to make statements in flat 
contradiction to what must have been easily verifiable obser- 
vations. And when such boys read books on the Middle 
Ages, their feeling is again one of amazement that the centuries 
which produced such magnificent art, architecture, and ima- 
ginative literature should have been so utterly incompetent in 
science. The ordinary mediaeval writer * seems to have used 
his own observations but seldom; he accepted the wildest 
assertions without troubling to confirm them, even when the 
simplest appeals to experience would have confounded them. 
Mediaeval writers on science were content to copy what they 
found in the relics and pretended relics of the science of classical 
times; much of it reached them at third hand through Latin 
versions of Arabic translations from the Greek. Not only 
Chaucer but even Shakespeare and Milton were infected by 
it. 

Let the boys appreciate the important fact that the men- 
tality of any given age springs from the particular views of 

* Boys may usefully read selected passages from Professor Langlois's La Vie 
en France ati Moyen Age, Vol. Ill, dealing with the scientific writers of the age. 
Professor Langlois asks the question, " What scientific knowledge was at the 
disposal of the layman from the twelfth to the fourteenth century?" And he pro- 
vides the answer by quoting extracts rom eight of the best-known writers; e.g. 
The Bestiary or Lapidary of Philippe de Thaon; The Secret des Secrets, by Jofroi 
de Watreford and Servais Copala; the Roman de Sidrac^ The false science and the 
absurd science in those books are amazing. The writers evidently had a passion 
for the sensational and the fabulous; they had a blind supenAition for antiquity; 
and they were utterly lacking in any sort of critical power. 



388 SCIENCE TEACHING 

the world thaf are dominant amongst the educated sections of 
the community. 

Not the least important thing for boys to understand is the 
extreme difficulty of ensuring that the facts from which they 
reason are objective and untainted. On this point a lesson 
may profitably be given on Bacon's Iols\ and extracts from 
Lord Balfour's books and from Mill's Logic, on the same 
point, will repay reading. In short, the first elementary lesson 
in philosophy to learn is the necessity for trying to eliminate 
from evidence all forms of bias, in order that an objective 
judgment may become possible. Beliefs that are very strongly 
held may, of course, be mere prejudice: can we greatly blame 
a native of West Africa for scoffing at the statement that water 
may become solid? The second elementary lesson in philo- 
sophy to learn is that we are all prone to be deceived by our 
own senses, and to think we perceive in things qualities which 
do not really belong to them, qualities which are, in fact, purely 
the offspring of the mind. Nature is black and colourless, 
silent and scentless, though it is never at rest; it is our senses 
that confer upon it light and colour, sounds and odours, and 
our senses are all notoriously limited. 

About the real nature of perception how we come into 
cognitive contact with reality external to ourselves even philo- 
sophy fails to tell us very much. As for physical science, it 
simply takes the perceptual world as it finds it, at least as 
far as its different precepts are mutually consistent, and con- 
cerns itself merely to discover its structure and modes of 
behaviour. It is enough to tell the boy that we simply do 
not understand the nature of perception, and that therefore 
it is impossible to feel absolute confidence in the foundations 
of science, for these depend on our perceptions. 

Philosophy takes the concepts used by science, analyses 
them, and tries to determine their precise meanings and rela- 
tions. It tries to replace a mere hazy general familiarity by clear 
and accurate knowledge. Chemistry uses the idea of matter \ 
geometry that^of space, mechanics that of motion. The special 
senses are content with a rough and ready meaning of such 



PHILOSOPHIC FOUNDATIONS OF SCIENCE 389 

terms, just as far as is necessary for their own special purpose. 
Philosophy probes them farther, and calls upon their users 
to define them accurately. This is the real philosophy to be 
taught in the classy-room: a persistent cross-examination con- 
cerning all terms used and concerning all premisses which are 
made the basis of reasoning. 



Induction and Hypothesis 

For science, the most important department of philosophy 
is probably logic, but, until within quite recent years, logicians 
have not helped science very much. Instead of describing the 
actual methods by which science has advanced, and of extract- 
ing from those methods the logical rules which might be used 
to regulate scientific procedure, logicians have treated dis- 
coveries as mere illustrations of preconceived ideals of such 
procedure. Logicians have not been familiar with the practical 
details of scientific problems, and science has turned to logic 
in vain. The logical theory of proof has little or no bearing 
on the scientific process of discovery. 

But the modern logician has become alive to the necessity 
of revising his methods. He is now giving serious attention to 
the nature of induction, hypothesis, law, probability, and the 
like. 

Induction is a process very much more than attaching a label 
to a goodly number of similar instances. The key to it is to 
be found, says Professor Whitehead, in " the right under- 
standing of the immediate occasion^of knowledge in its full 
concreteness ". The immediate occasion must be observed 
completely, and reasoning must be used in order to call forth a 
general description of its nature. " Induction is the divination 
of some characteristics of a particular feature from the known 
characteristics of a particular past." From the particular occa- 
sion, inductive reasoning proceeds to the particular community 
of occasions, and, from the particular community, to the rela- 
tions between particular occasions within tha community. 

But this is not quite the whole story. It is true that physical 



390 SCIENCE TEACHING 

science is founded on observation and experiment, ana mat 
repetition implies some valid method of drawing inferences 
from experience, that is of induction, but no logician has ever 
yet succeeded in formulating a theory of valid induction that 
would obtain general agreement. Such continuing weakness 
has been described by Dr. Broad as a Icandal. Until the pro- 
blem of induction is solved, the foundations of science are 
necessarily insecure. This is another important point to 
impress upon the learner, though doubtless he has long ago 
been warned of the danger of jumping to conclusions. 

Hypothesis. There is no more important function of the 
science teacher than to keep clear in his pupils 5 minds the 
nature of the difference between fact and hypothesis. An 
hypothesis is nothing more than a mentally constructed 
mechanism invented to account for an obviously close relation- 
ship amongst a group of facts. It is always highly improbable 
than an hypothesis will be proved to correspond to objective 
reality. It is much more likely to be superseded some day. 
All the commonly accepted hypotheses of science the atomic, 
kinetic, electromagnetic, heliocentric, and evolutionary hypo- 
theses are all provisional, though they are supported by vast 
numbers of facts. They may be true, but we cannot say more. 
Once proved to represent objective reality, an hypothesis 
ceases to be an hypothesis and becomes a fact. But as long 
as it remains an hypothesis, it must ever be subjected to 
scrutiny, especially in the light of new facts. 

A Sixth Form boy sometimes asks whether, in view of the 
hypotheses of science beiijg nowadays so frequently superseded 
by others, science has ceased to represent that embodiment 
of certain knowledge that it was formerly considered to repre- 
sent, especially during the last quarter of last century. The 
question is a perfectly fair one, and the teacher must deal 
with it. 

When medievalism began to fade away before the gathering 
forces of the renaissance, science began to advance rapidly, 
and by the beginning of the seventeenth century it went 
ahead in leaps and bounds. The workers of this period in- 



PHILOSOPHIC FOUNDATIONS OF SCIENCE 391 

heriftd a ferment of ideas attendant upon the intellectual 
revolt of the preceding century, and it so happened that the 
period provided a number of intellectual geniuses adequate 
to the occasion: Bacon, Harvey, Kepler, Galileo, Descartes, 
Pascal, Huyghens, Boyle, Newton, Locke, Leibnitz think of 
them, and there was Shakespeare as well! Never before or 
since has the world produced a galaxy of such extraordinary 
talent almost at the same time. 

Try to make the boys realize what great work these great 
men did. Contrast the world's knowledge before and after their 
work was done. Show how very little material they had to go 
upon. Show how they worked. 

Should the Older Hypotheses be Discarded? 

So much was done by them, in fact, that their successors 
of the next 150 or 200 years had their hands full in applying 
the great principles formulated, in building up a superstructure 
on foundations so securely laid. Newton had said the very 
last word, and nobody dreamt of questioning him. Physics, 
and even biology, eventually settled down on a mechanist 
basis, expressed in such concepts as absolute position in space 
and an elastic solid aether. But gradually new facts forced 
themselves on men's notice, some of them the results of experi- 
ments so refined that Newton could never have dreamt of 
them. Accepted physical laws had to be examined, restated, 
even scrapped. It became evident that science is even more 
changeable than theology. We can no longer subscribe to 
Newton's beliefs; we cannot subscribS even to our own beliefs 
of ten years ago. Galileo said that the earth moves and that 
the sun is fixed; the Inquisitors said that the earth is fixed 
and that the sun moves; the Newtonian astronomers, adopting 
an absolute theory of space, said that both move. Now we 
say that any one of these three statements is equally true, 
provided that our notions of'** rest " and " motion " are fixed 
in the way logically required by the stateihent adopted. 

The last twenty years have, indeed, seen the foundations 



392 SCIENCE TEACHING 

of physics torn up, and the new structure is not yet completely 
built. The changes have come about not only by the press of 
new knowledge, but also, to a great degree, as the result of a 
keen examination of the fundamental conceptions of physics. 
As Professor Whitehead writes in Science anclthe Modern World, 
" the progress of science has now rt ached a turning-point; 
the stable foundations of physics have been broken up; the 
old foundations of scientific thought are becoming unintelli- 
gible. Time, space, matter, material, aether, electricity, 
mechanism, organism, configuration, structure, pattern, func- 
tion, all require reinterpretation. What is the sense of talking 
about a mechanical explanation, when you do not know what 
you mean by mechanics?'' 

But it would be a grave mistake to put things to boys as 
strongly as this, and to leave upon their minds the impression 
that our knowledge of science is entirely lacking in certitude. 
That Einstein has superseded Newton is true; that Newton's 
mechanics must be replaced by an entirely remodelled mechanics 
is also true. But this does not mean, and boys must not be 
allowed to think that it means, that Einstein is a greater genius 
than Newton. Einstein still looks upon Newton as his great 
master. Newton's laws covered all the facts available in New- 
ton's time; his laws have to be superseded simply and solely 
because they do not cover certain facts more recently discovered. 
The actual differences in practical life are negligible, so much 
so that the older mechanics is likely to hold the field, as far as 
school work is concerned, for many a long year to come. The 
important lesson for the boy to learn is that, all hypotheses 
being provisional, it is pfobable that Einstein's hypothesis may 
itself be superseded some time. It must be superseded if new 
facts come along that cannot be brought within its ambit. 

And, after all, the work of Einstein is not strictly com- 
parable with that of Newton. The two fields of thought are 
different. So far as the work of Einstein is relevant to that 
of Newton, it is simply a greater 'generalization, and a broaden- 
ing of the basis; it is just a case of further mathematical develop- 
ment. So generally: a great principle once established is 



PHILOSOPHIC FOUNDATIONS OF SCIENCE 393 

rarefy discarded altogether, but it is so modified that it rests 
upon a basis both broader and more stable. 

It was really Mach who paved the way for such positive 
advances as the theory of relativity and the quantum theory, 
and all science teachers should read Mach's Mechanics. A 
considerable portion ofc the book is within the scope of Sixth 
Form work. 



Is Mathematical Reasoning Trustworthy? 

There is a fundamental difference of intellectual attitude 
between, on the one hand, Einstein and those who, like Eclding- 
ton, think with him, and, on the other hand, the more typical 
English physicists as represented by Sir J. J. Thomson, Sir 
Oliver Lodge, and Professor Larmor. The latter school demand 
that any hypothesis must be so constructed that it represents 
a mechanism which can be clearly visualized; they demand 
a mechanical model of the physical universe, built in normal 
space and time. They distrust arguments concerning physics 
that cannot be followed up by the mind pictorially. Einstein, 
and probably the greater proportion of Continental mathe- 
maticians, make no such demand. If they start off with definitely 
established and unassailable premisses, they are content with 
subsequent rigorous analysis and deduction; and if competent 
critics agree that this mathematical reasoning is flawless, they 
accept the final result as unquestionably true. And if, as in 
the case of relativity, the result proves to be open to possible 
means of experimental verification, and if this verification is 
carried out and supports the result Arrived at mathematically, 
it is difficult to refute the contention that both the method 
and the result are as unassailable as the premisses. Still, it is 
probably a wholesome intellectual bias on the part of most 
English physicists to insist that they must always reason in 
such a way as if they were able to visualize the parts of the 
thing they are reasoning abcJit. In any case, it is best to pro- 
vide boys with means of picturing, say,* the structure of the 
atom, or an electromagnetic wave, or what n<Jt. If boys put 



394 SCIENCE TEACHING 

their exclusive confidence in mathematical formulae, their \vork 
may be good mathematics but it will inevitably be bad science. 
The reasoning will be wholly abstract, and this to immature 
minds is necessarily without real significance. 

Most of the original prejudice against Einstein's results was 
due to the impossibility of visualizing ft four-dimensional con- 
tinuum, or of the " warping " or the curvature of space-time. 
But an eminent mathematician has recently said that Einstein's 
gravitational field-equations, like Maxwell's electromagnetic 
field-equations, must henceforth be regarded as the most 
axiomatic fundamentals of physics; and that they cannot be 
questioned, and never will be questioned, any more than the 
multiplication table will be questioned. But is not this dog- 
matism a little rash? New discoveries have led to the dethrone- 
ment even of Newton. Impress upon pupils the need of 
caution as to the final acceptance of any hypothesis, no matter 
whether the hypothesis is built upon experimental data and 
assumes a concrete form, or whether it emerges as an abstrac- 
tion from the work of mathematicians. 

As regards biological concepts, teachers should be on their 
guard against a too ready acceptance of the simply constructed 
Victorian mechanisms that seemed to explain biological pheno- 
mena so satisfactorily. Biology has yet to come to terms with 
psychology and to abandon the hopeless attempt to derive 
conscious behaviour from tropisms and conditioned reflexes, 
regarded as purely physical happenings. Psychology is not 
yet able to give biology very much help, and it therefore 
behoves biology to wait. 

Inspire boys to must&r up the courage to say, " we don't 
know ", " we cannot understand ", " the evidence is incon- 
clusive ". Tell them, and tell them again and again, that 
science is no longer sure. 

Non- demonstrable " Proofs " 

Should a Sixth Form course include the serious considera- 
tion of phenomena of doubtful authenticity? Take, for 



PHILOSOPHIC FOUNDATIONS OF SCKNCE 395 

instartfce, the question of " dowsers " and w&ter-divining. 
Science has not yet been able to pronounce a verdict ex cathedra 
on the source of the mysterious force which dowsers are said 
to possess. Should we therefore remain agnostic and pooh- 
pooh its existence altogether, or should we label it fraudulent, 
or should we regard it fc> a miraculous happening? Firm faith 
in the hazel twig has been expressed by many eminent public 
men. In the recent work on the foundations of St. Paul's 
Cathedral, the contractors used a diviner to determine the 
position of water under the crypt. The Department of Public 
Works in Brisbane have employed a Government water-finder 
for at least two years. So has the Bombay Government. 
Directors of railway companies, and engineering, architectural, 
industrial, and commercial concerns are numbered among the 
faithful. On the other hand, science is undoubtedly divided 
over the question. It may be that owing to a kind of involun- 
tary, and at present inexplicable, reflex muscular action, the 
movement of the hazel twig held in the hands does enable 
some few sensitives to detect subterranean supplies of running 
water in places where there are no surface indications of its 
presence. This is not a place to pronounce an opinion, for or 
against, on the question of water-divining, but the lesson for 
the boy to learn is that, whenever claims for the existence 
of a new phenomenon are put forward, it is the business of 
science to investigate it; and that science must be extremely 
cautious in basing conclusions on negative results. Science is 
stultifying itself if it pronounces judgment before considering 
ascertained and ascertainable facts, if such facts there are. 
Science has rightly condemned such charlatans as phrenolo- 
gists, physiognomists, astrologers, and the like, but it has no 
right to condemn until it has investigated. 

Then there is the question of psychical research. School 
boys are constantly asking questions about it, and embarrassing 
questions, too; and science masters must be prepared with 
reasoned answers that will give at least some measure of satis- 
faction. 

Psychical research must, of course, be clearly distinguished 

(E72) 27 



396 SCIENCE TEACHING 

from spiritisil Psychical research purports to be the v study 
of supernormal phenomena, and not only such physical pheno- 
mena as telekinesis, the production of sounds and of psychic 
lights, and the formation of ectoplasm, but also such mental 
phenomena as clairvoyance and telepathy. Lodge and Richet 
are admittedly psychic researchers of the front rank, but, with 
precisely the same facts to go upon, the two have come to 
diametrically opposite conclusions. Lodge has come down 
definitely on the side of spiritism, being convinced that sur- 
vival is proved by a rational interpretation of the facts. Richet 
interprets the facts from an entirely different standpoint, and 
is irrevocably opposed to the spiritistic hypothesis. Indeed 
he holds that the hypothesis is actually disproved by some of 
the very facts of psychical research. 

The lesson for the boy to learn is the necessity for being 
extremely cautious in coming to conclusions about things con- 
cerning which recognized authorities disagree fundamentally. 
The boy may also rightly be taught to have scant respect for 
a man who " has never in his life been to a seance and never 
intends to go to one ", and yet treats with contumely those 
who are earnestly trying to get at the actual facts. The opinion 
of any man, however great, or of any body of men, however 
influential, on a subject which they deliberately refuse to 
investigate, either because it does not interest them or because 
of a preconceived idea that the phenomena involved are fraudu- 
lent, is necessarily worthless, and this every boy should clearly 
understand. It is a sad commentary on human nature that those 
men of science who take up the study of psychical research, 
even in these days of generous tolerance, run the risk of losing 
caste and even of suffering persecution from their old colleagues. 
Science workers who denounce the persecutions of the Middle 
Ages stultify themselves when they calmly take the very chair 
from which they drove the mediaeval church. Psychical pheno- 
mena may be of a wholly fraudulent character: the only con- 
cern of science is to undertake an unprejudiced investigation, 
and then, but not fall then, to pronounce judgment; and that 

* " Spiritualism " in this sense is, of course, an absurd term; 



PHILOSOPHIC FOUNDATIONS OF SCIENCE 397 

judgment, to be scientific, must be cold and uncoloured. 

Tell the boy frankly that there are aspects of human per- 
sonality about which science fails to give a satisfactory explana- 
tion; that the richness of reality seems to be as inexhaustible 
in the unplumbed depths of personality as in the manifestations 
of the external world.* 

The science teacher is sometimes asked by his boys to 
expound different points of theology, more especially points 
arising from the interpretation of the biblical narrative. It is 
unwise to burke such questions, and it is a good plan for 
science teachers and the teachers of religious instruction occa- 
sionally to compare notes. A generation or two ago it was the 
fashion in certain science circles to be aggressively rationalist 
and dogmatic. Gradually the attitude gave way to a milder 
agnosticism which, in its turn, is being replaced by a general 
admission that the little knowledge we possess is as nothing 
compared with our still profound ignorance both of nature and 
of ourselves. 

Both science teachers and teachers of religious instruction 
will probably agree that pupils may properly be told, on the 
one hand, that credulity is no longer looked upon as a virtue, 
doubt no longer condemned as a sin; on the other hand, that 
in biblical and liturgical literature there are many crudely 
expressed thoughts, but that, in spite of this crudity of expres- 
sion, the thoughts themselves may enshrine profound truths 
that very few people are really competent to plumb. Some 
crudity of expression is almost inevitable whenever an attempt 
is made to clothe in words for popular understanding some 
particular idea, whether the idea belongs to science, or to 
philosophy, or to theology. 

The biological theory of the evolutionary origin of man 
seems now to prevail generally among educated members of 
the English churches, clerical as well as lay, but no systematic 
attempt is being visibly mad^ to modify the traditional dog- 
matic system, in view of the new knowledge which so pro- 
foundly affects it. Yet the pressing need of sjich theological 
restatement can escape no reflective person. It is, however, 



398 SCIENCE TEACHING 

certain that the new doctrinal view is best disseminated with 
extreme caution and reserve, and that any authoritative far- 
reaching restatement of theological dogma would at present be 
dangerous. Progress is indispensable, but caution is indispen- 
sable too. And in the Sixth Form this is the best note to strike. 
The boys should know that the attitlide of men of science 
towards their theories has undergone a profound change in 
the last twenty or thirty years. There is now a much greater 
caution. The hostility of laymen towards science is therefore 
tending rapidly to diminish, though there are still a few whose 
natural cast of mind is alien to the garnering and classifying 
of undisputed facts, and who, instead, repose confidence in 
intuitional modes of apprehension. Men of science are now 
the first to admit that the object of their theories is not to 
reveal the real nature of things, but to co-ordinate the physical 
laws revealed by experience. Philosophy goes farther, beginning 
where science leaves off. 

An Outline Lesson on Inference 

Here is an extract from Scientific Method, typifying in out- 
line the kind of lesson contemplated in this chapter. 

" Inference " is a very ambiguous word. " When we infer 
one fact from another or others, we believe that fact ' by reason 
of ' our belief in those others; and when we prove one fact 
by means of another, exactly the same expression is commonly 
used. In both cases there is ' reasoning ', and, accordingly, 
both that from which the, inference is drawn and that on which 
the proof is based, are indiscriminately called, in popular 
language, the reason. We reason when we proceed from pre- 
misses to conclusion, arriving at new truths by means of old 
ones; and we reason when, having already an assertion before 
us, we produce arguments to support it, even if such arguments 
be then for the first time thought of. Again, the term ' pre- 
misses ' is sometimes used for the grounds of proof, and some- 
times for the d(ita of inference', ' conclusion ' sometimes means 
that which is discovered and sometimes that which is proved" 



PHILOSOPHIC FOUNDATIONS OF SCIENCE 399 

Inferences are of very varying degree. They* may be merely 
our first vague guesses; they may be the final and certain results 
of the most careful inquiry. 

It would be Convenient to restrict the term Inference to 
the process of reaching a belief, and to speak of a Conclusion 
following from its " premisses " or " data "; and to regard 
Proof as the process of establishing a belief on a firm foundation 
after it is already somehow reached. Thus, in the case of 
proof we should speak of an assertion " guaranteed by " its 
" reasons ", or " resting upon " its " grounds ". The problem 
of Proof is thus narrower and more definite than that of Infer- 
ence. Instead of asking at large, " What conclusion may be 
drawn?" Proof asks, " Is such and such a reason warranted?' 1 

It is evidently immaterial to an argument whether the con- 
clusion is placed first or last. But a premiss placed after its 
conclusion is usually called the reason of it, and is introduced 
by a causal conjunction (since, because , &c.). The illative 
adverbs (therefore, &c.) designate the conclusion. 

Perplexity often arises from the fact that these conjunctions 
and adverbs have also another signification, being employed 
to denote, respectively, cause and effect, as well as premisses 
and conclusion. For example: 

(i) The soil is rich because the trees on it are flourishing; 
or (2) The trees are flourishing and therefore the soil must be rich. 

In both examples the italicized words denote the connexion 
between premisses and conclusion', for clearly the luxuriance of 
the trees is not the cause of the soil's fertility but only the 
cause of my knowing it. But if I say: 

(i) The trees flourish because the soil is rich; 
or (2) The soil is rich and therefore the trees flourish; 

I use the same words to denote the connexion of cause and 
effect , for in this case the luxuriance of the trees, being evident 
to the eye, would hardly need to be proved, but might need to 
be accounted for. 

In some cases the cause is employed to prove the existence 
of the effect. For instance, when from favourable weather 



400 SCIENCE TEAUfiiNG 

anyone argues* that the crops are likely to be abundant', 4 the 
cause and the reason coincide. And this contributes to their 
often being confounded together in other cases. 



CHAPTER XXXVII 

Science and Humanism 

It is an important part of the work of the science teacher 
to leave on the mind of the boy the definite impression that, 
despite appearances, there is no natural antagonism between 
science on the one hand and humanism on the other, 

It was Mr. John Galsworthy who said: " We have made by 
our science a monster that will devour us, unless by exchanging 
international thought we can create a general opinion against 
the new powers of destruction so strong and so unanimous 
that no nation will care to face the force which underlies it." 
It is, indeed, a common thing for people to look upon science 
as a disturbing influence in human affairs, and to sigh for the 
simple life away from the restless spirit of inquiry into all 
things visible and invisible in the universe. During the last 
fifty years there have, of course, been more scientific dis- 
coveries and applications than in the whole previous history 
of the human race; and we may be on the threshold of develop- 
ments by which forces will be unloosed and powers acquired 
beyond those hitherto known. Whether these should be used 
to promote social well-being and international amity is not a 
question for science but for the public and its leaders. When 
at the Guildhall Mr. Baldwin urged that more pains should 
be taken to apply the methods of science to human problems, 
it was obvious that he meant, not the development of poison 
gases and high explosives, but the principle of facing facts 
honestly and fearlessly, and of basing just conclusions on them. If 
sound principles of progress are to be determined, the methods 
applied to social problems must be the methods of science. 

Sixth Form pupils should be taught that modern civilization 



SCIENCE! AND HUMANISM 4 oi 

is rdcflly built on science, and that almost all industrial develop- 
ments had their origin in principles established by investi- 
gators who were working purely for the advancement of natural 
knowledge. Faraday's discovery of the principle that a moving 
magnet may create a current of electricity in a coil of wire 
near it led to the construction of the dynamo and to the birth 
of the great industry of electrical engineering. All the pure 
copper required for electrical purposes is produced by elec- 
trolysis; so with aluminium; and the principles of this process 
were discovered during scientific investigation by Davy and 
Faraday. Examples of discoveries and their subsequent appli- 
cations may be cited in almost any number: Moissan, the 
electric furnace, and the enormous production of steel; the 
discovery of X-rays and their employment in surgery and 
other arts; the manufacture of liquid air, and modern refri- 
gerating machines; the metal tungsten and the manufacture 
of high-speed tool-steels; chromium and stainless steel; thor- 
ium and cerium and gas-mantles; argon and gas-filled electric 
lamps; neon and the pink glow-lamps of illuminated adver- 
tisements; helium and the inflation of dirigibles; and so on 
indefinitely. Let the boy understand that before things can 
be made in this way they must be discovered, and that it is 
the particular function of science to reveal them. Every new 
scientific discovery, however remote at the moment it may 
seem from the ordinary practical needs of life, may be seed 
destined to produce a mighty tree. The scientific investigator 
discovers, the engineer or inventor recognizes and applies the 
discovery, the manufacturer makes it commercially profitable; 
and it is the business of the community to see that it is used to 
promote social welfare. Progress is inevitable, and whether this is 
accompanied by increased happiness or not depends on ourselves. 
But the history of science is by no means a record of steady 
progress. It was born amongst the Greeks who made great 
advances in mathematics, astronomy, and medicine, but their 
backwardness in invention \^as due to' their adoption of a 
doubtful standard of values. It was tlie Greeks who taught 
themselves to think that it was a finer thing {o be an orator 



402 SCIENCE TEACHING 

than to be a scientific investigator. The Romans were no very 
great admirers either of originality or of intellectual progress, 
and after the time of Galen there is a barren scientific waste of 
more than 1000 years. During the Dark Ages, with their long 
orgy of superstition, massacre, and pillage, the general barbar- 
ization of the world was inevitable, a result which neither Hellen- 
istic philosophy nor Catholic Christianity did much to check. 

The materialistic trend of science in the nineteenth century 
was the consequence of its rather one-sided development. 
Biology advanced far more quickly than psychology, and physics 
and chemistry in their turn were ahead of biology. But the 
tendency to reduce life to mechanism is now being abandoned 
in response to protests from science itself, and the problems 
of conscious life are now seen to involve such profoundly 
difficult questions of a metaphysical character as to seem in- 
soluble. The former arrogant claims of science to infallibility 
have passed away, though there are still with us a few sturdy 
representatives of the old school almost as intolerant as were 
the Spanish inquisitors. 

School boys should be taught to exercise caution in thinking 
that science is likely to bring in the millenium. Can it, in fact, 
be maintained that motor-cars and wireless telegraphy and tele- 
phony, synthetic dyes and ferro-concrete skyscrapers, are mak- 
ing men better or happier? By saving the unfit, is medical skill 
raising the standard of the race? If tanks and poison-gas, air- 
raids and submarine sinkings, be weighed against field sanitation 
and plastic surgery, did science make the last war less terrible 
or more terrible? We now know that civilizations long since 
extinct attained remarkable levels of progress; are we not 
then justified in feeling doubt about the fate of the present 
order of things? Can science save us? The fact is that science 
has provided the tools of material progress but has not directed 
their use. Apparently there is no country in the world where 
the opinion of science is decisive in any matter affecting the 
welfare of the people; and the last word whether science is 
to be used to advance or to check the interests and the happi- 
ness of the community rests with the politicians. 



SCIENQJ AND HUMANISM 403 

Compared with the training of a business man, a training 
in science is almost a handicap. A successful business man, 
or, even more so, a politician, owes his success almost entirely 
to his powers of divining the wishes and thoughts of his fellow- 
men. But a man of science spends his time in dealing with 
an inanimate world ^hich cannot be influenced by tact, per- 
suasive powers, or individuality. In fact, the inexactitudes 
and tactful misrepresentations so characteristic of the business 
and political world are exceedingly distasteful to a man trained 
in the clear honesty and rigour of scientific thought; and when 
he is engaged in delicate negotiations of any sort, he is at a 
positive disadvantage compared with his commercial fellow- 
men, and is apt to be overmatched if not overreached. The 
trained man of science is likely to be much less tactful and 
much less persuasive, and will probably be a worse judge of 
character than a man who has spent an equally strenuous 
number of years either in persuading people to buy something 
they do not really need, or in n taking the worse appear the 
better reason. 

Then is a man of science merely an intellectual machine, 
perfectly honest though rather stupid in his human relations? 
Has he no claim to culture? 

Inasmuch as science has changed the whole background of 
our thought by giving us a new knowledge of man's origin 
and place in the universe; inasmuch as every branch of human 
thought feels the influence of this new knowledge; inasmuch 
as science has made the outlook of our grandparents and the 
very postulates of their thinking incredibly remote: assuredly 
science has a claim for a prominent place in the sun. 

We may ungrudgingly admit that, as an instrument of 
education, science cannot replace what are traditionally called 
the humane studies. But knowledge of scientific truth and 
appreciation of scientific method are the very foundations of 
modern humanism, and, without them, human thought would 
progressively degenerate. "Science has practically freed the 
civilized world from the thraldom of baSe superstition; and it 
has banished irrational fear. 



404 SCIENCE TEACHING 

Inasmuch as our national shortcomings are mainly of an 
intellectual character, it is as much the business of the science 
teacher as the teacher of any other subject to make boys con- 
scious of them. A boy very naturally, perhaps quite rightly, 
takes pride in race, but of course his pride is steeped in pre- 
judice. Grant him our readily recognized national merits our 
sense of right and wrong, our justice, our tolerance, our enter- 
prise, our moderation. But on the other side? our distrust 
of ideas, our tendency to belittle the trained and disciplined 
reason, our incurable sentimentality. Sting the boys into a 
full realization of the fact that we are the intellectual inferiors 
of many of our Continental neighbours. Shame them into the 
sense of the further fact that as a nation we are too lazy to 
think. Remind them that, for instance, all Asia is at last intel- 
lectually awake, and that therefore it behoves them to learn to 
think, to think hard, to think of the future. 

Impress upon them that the judgments of science are 
usually judgments of facts and not judgments of human values, 
and that therefore their special work in science requires supple- 
menting by a careful study of humanism; in short, that they 
must read widely from the great masterpieces of literature. The 
data of human values cannot be isolated and analysed as the 
data of science can be isolated and analysed. Human values 
are inseparable from time and change. If we are ever to under- 
stand the causes of the clashings of men's motives, we must 
get outside the laboratory, and study men. Not infrequently 
students of science fail to realize that the importance of such 
a study is supreme. 



" Trace science then, with modesty thy guide: 
First strip off all her equipage of pride; 
Deduct what is but vanity, or dress, 
Or learning's luxury, or idleness; 
Or tricks to show the stretch of human brain, 
Mere curious pleasure, ^r ingenious pain; 
Expunge tjie whole, or lop the excrescent parts 
Of all our vices have created arts; 
Then see how little the remaining sum" 



PART IV 
ACCOMMODATION AND EQUIPMENT 

These suggestions may help science teachers who are 
responsible for giving advice on the fitting up of laboratories 
and on the provision of equipment. 

It must be borne in mind that even after laboratories have 
been built and initially equipped, a considerable annual expendi- 
ture on upkeep is necessary. If books for the science library 
are to be included, the total annual expenditure on science 
equipment is likely to be in the neighbourhood of nine or ten 
shillings per every pupil in the school. School authorities natur- 
ally raise objections to spending more than about 20 on any 
single piece of apparatus, and it is a good thing to make an 
appeal, every three, four, or five years, to the friends of the 
school for subscriptions to cover the cost of the few desirable 
items likely to be listed at 30 or 40 or more. The necessary 
instruments for a school observatory will almost certainly have 
to be obtained in this way. 



CHAPTER XXXVIII 

Laboratories and Equipment 

Laboratory Accommodation Generally 

Science masters who have the advantage of collaborating 
with the school architect when a new science block is pro- 
jected will have themselves to blame for any imperfection that 
may show itself later. There are now about the country so 
many well built, fitted, and equipped laboratories that there 
is no longer any excuse for providing new laboratories which 
will not turn out to be a success in the working. The Board 
of Education, or the Science Masters' Association and the 
Association of Women Science Teachers, will doubtless always 
be willing to give the names of schools where approved labora- 
tories may be inspected, and a science teacher who goes on such 
a pilgrimage will be able to advise the school architect over 
the hundred and one details which are so important from the 
teaching point of view. Beware of accepting stock designs 
from the manufacturers. 

Certain main principles will occur at once to every science 
teacher. In order that vibration may be reduced to a minimum, 
all physical laboratories should be placed in the basement, 
or at least not higher up than the ground floor. To ensure 
the efficient ventilation of the whole science block, chemical 
laboratories should be placed on the : top floor, though it has 
to be remembered that this will entail additional cost in the 
plumbing, a fact which may make the school authorities 
grumble. Efficient ventilation is, however, essential. So is 
adequate lighting: and the windows should be so placed that 
they face neither the teacher nor the pupils. Drainage, sink 
accommodation, water supply, gas, and electric current, may 
never prove quite satisfactory unless tietails are carefully 
thought out beforehand. The drainage is particularly liable 

407 



408 SCIENCE TEACHING 

to give trouble, especially in chemical laboratories where there 
are necessarily numerous taps and sinks. Let the waste, from 
each bench-sink, drain through a vertical pipe into an open 
half-channel (or a V-shaped channel) having a slight fall, 
running the whole length of the bench, and emptying into a 
large trap at the bench end, this trap again emptying into a 
half channel under the floor, leading to the wall exit. Arrange 
for the half channels to be easily opened for inspection and for 
cleaning. The only closed pipes in the laboratories should be 
the short straight pieces from the sinks. Remember that 
rubbish will go down the sinks, and that therefore stoppages 
are inevitable if closed pipes are used. 

Let each main laboratory be large enough for a whole 
class of thirty. It is wholly unnecessary for classes always to 
be divided for practical work. If there is an intelligent labora- 
tory assistant available (as there ought to be), who can go 
round and guide the pupils in their manipulative difficulties, 
a science teacher ought to be able to cope with a class of 28 
or 30 pupils, in any elementary lesson. 

In laboratories with double benches, where the pupils are 
back to back, the gangways should be 4 feet wide. If the 
benches are single, a 3-foot gangway is wide enough. 

Central benches are always advisable for main work, but 
side benches for special types of work are useful in laboratories 
of all kinds. 

Laboratories should be so planned that the total area of 
the room divided by the number of pupils to be accommodated 
is 30 square feet. Thus for 30 pupils a laboratory 36 feet by 
25 feet is necessary. This allows room for a small demonstration 
table for the teacher. Short demonstrations in the laboratory 
are, of course, often necessary, but longer full-period demon- 
strations are best given in the lecture-room. 

A small school of 150 pupils will have to manage with one 
laboratory for all purposes. When the number approaches 
200, a second laboratory is indispensable, and then separate 
physical and chemical laboratories become possible. If, in a 
school of 200, biology has to be taught, the physical or the 



LABORATORIES AND EQUIPMENT 409 

chefikical laboratory must be used, according to the kind of 
work to be done; for experiments requiring the use of much 
water, the chemical and not the physical laboratory should be 
used. In large schools where elementary and advanced physical 
laboratories, elementary and advanced chemical laboratories, 
and a separate biological laboratory, are provided, the science 
work can naturally be organized much more effectively. 

Lecture -rooms 

All large schools should have at least one good-sized lecture- 
room, containing a teacher's demonstration table, with gas, 
current, water, and sink, and with ample drawer and cup- 
board accommodation. A spacious and properly ventilated 
fume-chamber within the wall between the lecture-room and 
preparation-room, and either a prepared white wall-surface 
behind and above the blackboard or a roll-up white linen 
sheet, for lantern purposes, should also be provided. The 
lantern should be a fixture at the back of the room, but it is 
useful to have a second and smaller lantern at the left end 
of the bench, and a small screen on the wall to the right of 
the bench, available for the teacher's occasional use during the 
course of an ordinary lesson. The demonstration table should 
be on a low platform; otherwise the pupils in the front row 
may not see what is going on. If rising tiers of seats are used, 
4-inch risers are amply sufficient. There is no point at all 
in having the back rows of pupils high above the ordinary 
floor-level, breathing the vitiated atmosphere in the upper part 
of the room. 

A lecture-room should provide 14 square feet of floor 
space per pupil. But if the room is designed for combined 
classes, 12 square feet per pupil is sufficient. In those schools 
where a lecture-room cannot be provided, a demonstration 
table should be placed in one of the class-rooms. 

For all the commoner demonstration-table experiments, a 
separate outfit of apparatus should always be ready for use, 
kept in allotted places in the preparation-roOm. 



410 SCIENCE TEACHING 

Preparation -rooms, Balance -rooms, &c. 

A preparation-room communicating with the lecturq-room 
by means of a large-sized fume-chamber 19 the intervening 
wall is very useful. The laboratory assistant should keep the 
sashes and sash-cords, on both sides of this cupboard, in good 
working order, and he should see that the ventilating gas-jet 
is alight before a lesson begins. The cupboard, drawer, and 
shelf accommodation of both the preparation- and the store- 
rooms should be carefully planned out, and waste of space 
thus avoided. 

Opinion has now definitely crystallized against the use of 
a separate balance-room for elementary work. A slate-slab, 
or a rigid bench, fixed against one of the long walls of the 
elementary chemical laboratory is now preferred, balance cases 
being, of course, provided. The supervision of a separate 
balance-room is not always possible, crowding is inevitable, 
and discipline is seldom what it should be. But the few fine 
balances used by the Sixth Form should always have a special 
home of their own, and a small well-lighted room should be 
given up to them. 

It is a good plan to provide all Middle Form boys with 
boxes of fractional (German silver or aluminium) weights for 
their exclusive use for the term. At the end of the term the 
boxes should be delivered up, all lost weights paid for, and 
replenished from stock for the next term. 

If the subject of light is to be taken up seriously, a separate 
dark room is indispensable. Means should also be provided 
for darkening both the physical laboratories and the lecture- 
room. Black blinds fixed at the bottom of the windows are 
to be preferred. 

Chemical Laboratories 

For elementary chemistry, single benches are the best, 
and they should be qu'ite free from shelves. The few necessary 
bottles of reagerKs may be kept on a slab of glass let into the 



LABORATORIES AND EQUIPMENT 411 

back of the bench, with a 2 -inch-high ledge behhid, to prevent 
the bottles from being swept off by passers-by. Remember 
the tendency of the stoppers of the bottles of sodium and 
ammonium hydroxide and sodium carbonate to become fast; 
rubber stoppers are better than glass; if glass, then cover with 
paraffin. 

The sinks in the benches should be large enough for use 
(with bee-hives) as pneumatic troughs, and should therefore 
be provided with Doulton's perforated plugs. Separate pneu- 
matic troughs are expensive, unnecessary, take up much bench- 
space, and tend to make the benches very wet and messy. 
The water-taps should be high enough to allow the placing of 
large beakers under them, but not so high that splashing may 
become a nuisance. 

Let the bench-tops overhang the drawers and cupboards 
underneath, sufficiently for pupils to sit in comfort. Let there 
be space underneath the cupboards for the toes, again for the 
purpose of comfort (but see that this shallow dark space is 
periodically cleaned). Arrange the bunsen connexions so that 
the taps cannot be accidentally turned by people passing them. 
Provide recesses for stools; also for rubbish bins, and see that the 
bins are cleared and cleaned periodically. And so on, and so on. 

Each pupil should have 3 feet 6 inches of running length 
of bench, and 2 feet of width; a bunsen connexion to himself, 
and a sink which he shares with one other boy. Let each cup- 
board and each drawer at every working place be divided up 
in such a way that each space contains its specified article 
and nothing else. An open cupboard or drawer should show 
at a glance if everything is there and in its proper place. All 
broken and worn-out articles should be shown to the teacher 
or to the laboratory assistant, replaced, and a record made. 
A small fine should follow a careless breakage, the fines being 
handed over to the science library. Let every pupil have a 
list of his apparatus posted up in his cupboard, and let every- 
thing be inspected and checked every term. 

A combustion hood may with advantage run the whole 
length of one end of the chemical laboratory, and all experi- 

(K72) 28 



4 i2 SCIENCE TEACHING 

ments in which noxious fumes are given oh suumu uc worked 
under it. See that it is efficiently ventilated. Let the Kipp 
cupboards be large rather than small; see that the sashes run 
easily; let the flames feeding the ventilation shafts come from 
a burner placed vertically, not horizontally: laboratory fires 
have been rather frequent because of neglect of some kind of 
safety-flame arrangement. 

Side-shelf accommodation for special reagents should be 
ample; so should cupboard accommodation for chemicals. Let 
one small cupboard be provided with a Chubb 's lock, to contain 
the costly and dangerous items. Even phosphorus and sodium 
are best kept locked away. (Law suits, consequent upon labora- 
tory accidents, are by no means unknown.) Let all reagents be 
properly labelled and be arranged in a fixed order, perhaps 
alphabetically. 

A special cupboard of the cabinet type, divided into com- 
partments for cork-borers, corks, files, pliers, &c., for general 
purposes is useful. 

Steam-baths, a still, &c., will, of course, be provided in all 
chemical laboratories. 

The laboratory assistant (not the boys) should be respon- 
sible for keeping all reagent bottles stocked. He should mark 
each label with the degree of concentration of the solution in 
the bottle. He should paint with paraffin, neatly, all newly 
stuck on labels. He and the bottle-washer should be respon- 
sible for keeping the laboratory in good order and scrupulously 
clean, also for reporting carelessness of individual pupils. An 
ill-organized and untidy laboratory tells a visitor at once that 
the responsible teacher is inefficient, for the ultimate responsibility 
is certainly his. 

An advanced chemical laboratory will, as a rule, be smaller, 
and provision will be made for the much larger number of 
reagents now required. Double benches four feet wide, with 
central sinks, will be the normal arrangement. A small off- 
room for the few necessary fine balances is also desirable. 
Sixth Form boys ought to be made personally responsible for 
much of the routine work of their own laboratory. They should, 



LABORATORIES AND EQUIPMENT 413 

for instance, make up their 'own solutions for volumetric work, 
as part of their ordinary training. 

Reference has already been made to the provision necessary 
in case of accidents, with instructions as to procedure. It is 
also a good thing to frame and place in a conspicuous position 
a few laboratory rules, to be gone over once a term in all Middle 
Forms. When heating a test-tube or boiling-tube, incline it 
away from self and neighbours; never let the flame touch that 
part of the tube above the contained liquid; round the sharp 
edge of a glass tube before pushing through a cork; never 
handle sodium or phosphorus with the fingers; never lay down 
the stopper of a reagent bottle; and so on. 

Physical Laboratories 

Ample bench space is essential for experiments in physics. 
The working benches should be of the nature of plain strongly 
framed, rigid tables, about 2 feet 9 inches high, centrally placed, 
with tops of hard well-seasoned wood, unpolished. The double 
table should be 3 feet 6 inches or 4 feet wide, with a running 
length of 3 feet 6 inches for each boy; and there should be a 
four-way bunsen connexion for every four boys. The 7 feet 
of running length is certainly desirable for every two boys 
doing advanced work: in electrical experiments it sometimes 
happens that several large pieces of apparatus have to be con- 
nected together. Sinks in the benches are undesirable, but 
there should be at least two large sinks in opposite corners 
of the room, with water-supply and yaste, and long draining- 
boards. Low-voltage current, converted from the main, should 
be available for the pupils' use. (There is a very useful article 
in the School Science Review for June, 1925, by Mr. G. W. 
Baker, giving full details of the " Rectification of Alternating 
Currents " for school laboratories.) Adequate side-bench 
accommodation is also desirable, especially for the best 
galvanometers and other instruments the accuracy of which 
may be impaired if they are frequently moved about. 
Heat experiments in which much steam or vapours are given 



414 SCIENCE TEACHING 

off should be performed in the elementary chemical laboratory. 
Any risk of injury to physical apparatus should be foreseen and 
guarded against. 

Cupboards for storage must be large, m view of the large 
size of much of the apparatus. In the elementary physical 
laboratory, apparatus should, as a rule, be sufficient for a 
whole class to be working the same experiment at the same 
time, two boys being told off to use the same set of apparatus. 
In an advanced physical laboratory, the work is necessarily 
organized differently, the requisite apparatus being too expensive 
for many sets to be purchased. 

Unless there is a separate mechanics or engineering labora- 
tory, overhead rails in the elementary physical laboratory 
should be provided, fitted with clamps, &c., for suspension 
and pendulum experiments. But in all large schools for boys, 
a separate mechanics laboratory is advisable. Then mechanics 
will receive the attention it demands, and there will be room 
for working models and other special apparatus. 

A mercury bench is a useful adjunct to any physical labora- 
tory. So is a soldering bench. 

If the school is provided with workshops, breakages and 
the making of simpler forms of mechanical and physical appa- 
ratus may be entrusted to the responsible instructors. If not, 
one end of the elementary physical laboratory (unless a separate 
room can be provided) should be fitted up with a carpenter's 
bench, a smith's vice, and a bench for soldering, brazing, and 
glass-blowing. 

If often happens th?t the same lecture-room is used for 
demonstrations in both chemistry and physics, and there is 
sometimes a clash of opinion whether the charts on the walls 
should be representative of chemical or of physical processes. 
It is doubtful wisdom to put charts of any kind on the walls. 
They are rarely or never looked at attentively. It is better to 
bring them out when they are t9 be discussed. It is preferable 
to decorate the wall space with portraits of the world's great 
science workers, past and present (Nature publishes a large 
number of them). 



LABORATORIES AND EQUIPMEMT 415 

Biological Laboratories 

Few schools have more than one biological laboratory, and 
commonly that is used mainly for botany. 

The first essential of a botany laboratory is good light. 
The room should have an aspect that will ensure plenty of 
sunlight for growing plants. The main benches should be 
central and consist of strongly made tables with tops of well- 
seasoned wood, unpolished. A side bench 2 feet wide should 
run the whole length of one side of the room, under the windows; 
it is useful for physiological experiments, for other experiments 
that require a specially good light, and for work with the 
microscope. At least two large sinks, with water and waste 
and good draining-boards, should be provided at opposite 
corners of the room. A demonstration table, with sink, water, 
gas, drawer, and cupboard accommodation is also necessary. 
A glass-house as an annexe should be looked upon as an almost 
indispensable part of a botany laboratory. Failing that, a 
Wardian case (a glass case with an automatic heat regulator) 
should be provided; also special provision for germinating 
seeds. Ample provision of cupboards and shelves is necessary, 
and a special side bench 4 or 5 feet long with shelves above 
for reagents is very useful. A narrow shelf above the long side 
bench under the windows is useful for pot plants, &c. And 
of course a school garden is as necessary as a laboratory. 

The same room will, as a rule, be used for other biological 
subjects (zoology, physiology, &c.). 

The School Observatory 

School authorities generally look upon an observatory as a 
luxury and are disinclined to provide it. If an appeal to some 
generous friend of the school can be made successfully, and 
the cost of the necessary instruments thus met, the school 
authorities may perhaps be induced to find the money for a 
small domed building. The principal Instruments are an 
equatorial (say a 4^-inch), an altazimuth, and a' transit instru- 



416 SCIENCE TEACHING 

ment (say a 3 -inch), though the fi^st two are easily combined 
into one. Everything depends on the amount of money avail- 
able. 

Apparatus and Equipment 

Before making purchases, make out a list of experiments 
to be performed, and of principles to be experimentally demon- 
strated. Then differentiate between the experimental work 
to be done by the teacher himself, and that to be done by the 
pupils; and purchase supplies accordingly. 

In addition to the usual stock of apparatus for all kinds of 
elementary work, and the flasks, beakers, tubing, chemicals, 
reagents, &c., for everyday use, the following are some of the 
articles to be looked for in a well-equipped school. 

MECHANICS AND HYDROSTATICS (do not buy useless 
toys: the real things cost very little more): 

Fletcher's trolley (several). 

Atwood's machine (hardly necessary these days). 

Hick's ballistic balance. 

Kater pendulum. 

Young's modulus apparatus (for tension and for bending). 

Shear modulus apparatus. 

Machines, including substantial pulley blocks. 

Screw-jack. 

Crane. 

Roof-truss. 

Gyroscope. 

S. H. Motion apparatus. 

Moment of inertia apparatus. 

Geryk air-pump. 

Mercury pump. 

Barometer, on Fortin principle (about 10. A Fortin itself is 
too dear and is quite unnecessary for school work). 

Aneroid, with working parts visible. 

Bramah press. 

Model pumps in glass (use very gently). 

Boyle's Law (one standard apparatus for demonstrations, two 
or three of a simple form). 

Hare's apparatus (several: let tubes be varied as to bores, inclin- 
ation, &c.). 



LABORATORIES A*ND EQUIPMENT 417 

forking wooden models _of link-fnotions and pther parts of a 
steam-engine are useful. 



SOUND: 

Wave-motion apparatus. 

Savart's toothed whe?l (ratios 4, 5, 6, 8), and whirling table. 

Siren. 

Range of tuning forks. 

Electrically driven forks. 

Sonometers. 

Tyndal's resonator and bell. 

Resonance apparatus. 

Organ-pipes (various). 

Koenig's manometric flames apparatus. 

Kundt's tube. 

Sensitive flame apparatus. 

Chladni's plates. 



OPTICS: 

Common photometers. 
Electric photometer. 

Mirrors, various, including a kaleidoscope. 
Optically worked prisms. 
Fresnel's prism. 
Optical bench, accurate. 
Optical benches, rough. 

Lenses, a good stock, including achromatic combinations. 
Spectroscope. 
Spectrometer. 
Interference apparatus. 
Diffraction apparatus. 
Diffraction gratings. 
Newton's rings. 
Polarizing set. 

Optical lantern (a &V wx* v/pe). 
Sextant. 

Caustics mirror. 
Telescope. 

Microscope, common (an eye-piece and an objective, to take to 
pieces). 

Microscope, good quality, for magnification measurement. 



418 SCIENCE TEACHING 

HEAT: 

Coefficient of linear expansion of metals apparatus. 

Dulong and Petit's apparatus for coefficient of absolute expansion 
of mercury. 

Coefficient of air expansion (constant pressure ,j constant volume). 

Vapour pressure apparatus, various types, including Regnault's. 

Latent heat of steam apparatus. 

Gas liquefaction apparatus. 

Vapour density apparatus (Hoffmann's, Dumas's, Victor Meyer's). 

Boys's radio-micrometer (expensive: secure as a present; so with 
other very expensive items). 

Nobili's thermopyle. 

Langley's bolometer. 

Joly's, Bunsen's, and other common calorimeters. 

Clement and Desorme's specific heat of gases apparatus. 

Simmance-Abady gas calorimeter (expensive). 

Lewis Thompson's calorimeter (for evap. point of coal). 

Berthelot-Mather's calorimeter, with bomb (for calorific value 
of fuel) (expensive, because of high cost of platinum). 

Calendar's mechanical equivalent of heat apparatus. 

Pyroheliometer (expensive). 

Accurate thermometers. 

Sectional working models of steam-engine. (See under mechanics.) 

ELECTRICITY AND MAGNETISM: 

Magnetometers (various). 

Vibration boxes. 

Dip-needle (about 3, 105.). 

Clinometer. 

Prismatic compass. 

Primary cells in variety; accumulators. 

Standard cells: Weston normal, Daniell's, Fleming's. (Write 
to the National Physical Laboratory for uistructions for setting up 
standard cells of the Weston type.) 

Voltameters, various. 

Joule's calorimeter. ; 

Kohlrauch's apparatus for conductivity of electrolytic solutions. 

Galvanoscopes, sensitive and rough. 

Galvanometers, in large variety (common reflecting, sensitive 
dead-beat; sensitive ballistic; unipivot types; Ayrton-Mather's 
reflecting, with interchangeable ballistic and dead-beat coils). 

Ammeters and voltmeters, accurate and commercial (of good 
range). ; 



LABORATORIES AJND EQUIPMENT 419 

jyilliammeters and millivpltmeter. 
Combined ammeter and voltmeter, magnetic control. 
Combined ammeter and voltmeter, gravity control. 
Pojentiometers (dial and other patterns). 
Bridges, various (one with potentiometer). 
Resistance boxes and frames; lamp resistances. 
Post Office boxes. t 
Standard resistances. 
Rheostat; megohm; carbon resistance. 
Condensers, standard and common. 

Thermocouples; Nobili's thermopile; electrical pyrometer. 
Langley's bolometer. 

Induction coils, various. (A 6-in. spark coil for X-ray work, &c., 
cost over 20.) 
Geissler's, Crooke's, and Rontgen's tubes. 
Fluorescent screens. 

Dynamo and motor (small models will do, if a generating station 
can be visited). 

Thermionic valves. 

Wireless sets stock parts for making up. 

Quadrant electrometers j 

Torsion balance now almost a luxury. 

Wimshurst machine } 

CHEMISTRY: 

Balances and weights, common; the usual stock for Middle Forms. 

Sets of German silver (or aluminium) fractional weights, 3$. a 
set, in box with forceps, one set for each boy. 

Two or more fine balances for Sixth Form boys, to turn from 
200 gm. to T \y mgm. 

Two or more boxes of weights, 100 gm. to i mgm., and 50 gm. to 
i mgm., gilt or platinum plated. 

Still and condenser; or 

Battery of drying ovens and still combined. 

Vacuum still. 

Water baths. 

Filter pumps: Bupsen's, Korting's with vacuum gauge, common 
forms in variety. 

Fractional distillation tubes. 

Furnaces: crucible, muffle, combustion. 

Gas analysis apparatus: Stead's, Orsat Pryce's. 

Gas burettes and absorption pipettes. 

Apparatus for composition of HC1, NH 3 * NO, CO 2 , &c. 

Beckmann's depression of freezing-point apparatus. 



420 SCIENCE REACHING 

Beckmann's elevation of boiling-point apparatus. 

Nitrometers. 

Steel cylinders of gases: O, CO 2 , SO 2 . 

Standard flasks and graduated vessels (including a small number 
of standard burettes and pipettes verified and stamped at the Nat. 
Phys. Lab.). 

Platinum crucibles, foil, wire. (Present cost is very high; hence, as 
far as possible, substitute vitreosil.) 

Vitreosil apparatus: basins, crucibles, combustion boats, beakers, 
combustion tubing, watch glasses, reduction tubes; all acid-proof 
and heat-proof. 

\\t degree thermometers, i or 2. 

One Beckmann thermometer, reading to T J <y. 

Organic material including a plentiful supply of alcohol (a rebate 
of duty is obtainable). 

Useful: hot-water funnel for hot filtrations; double-slotted anti- 
parallax cards for slipping over burettes; draining-rack with pegs 
for test-tubes, &c. 

BOTANY: 

Microscopes with J-in. and -J~in. objective (Abbe condenser, 
polarizer, and mechanical stage unnecessary for all ordinary work). 

Microscopes, one or two of better quality (one T V oil-immersion 
objective should be available, but should be kept in the teacher's 
private cupboard). 

Hand and pocket lenses. 

Thermostat. 

Klinostat. 

Potometer. 

Osmosis and absorption apparatus, including manometers. 

Respirometer. 

Recording transpirometer. 

Photosynthometer. 

Auxograph. 

(Speaking generally, measurement experiments will be confined 
to the Sixth Form; for forms below, much of the necessary apparatus 
should be improvised.) 

ZOOLOGY: 

Dissecting dishes and instruments, one set for each pupil. (En- 
amel dishes 9 in. X 6 in. X ij in. are the best, with cork carpets held 
down by strips of lead.) 

Some form of freezing microtome. 



LABORATORIES /iND EQUIPMENT 421 

^{ivaria. 

Chemical apparatus ana reagents for physiology. 

For all forms of live material consult the nearest University 
Professor of Zoology. See also the advertisement columns of 
Nature. 

HUMAN PHYSIOLOGY: 

A human skeleton is useful. 

Anatomical models of the eye, ear, larynx, nose, and heart. 

Some forma of apparatus to show why air enters and leaves the 
lungs. A large bell-jar with a stretched sheet of thin rubber tied over 
the open end, and a cork through which pass two short glass tubes; 
to the lower end of one tube is tied an elastic bag which is thus sus- 
pended in the bell-jar; through the other tube, air is driven into the 
bell-jar. There are various forms of such apparatus obtainable 
from the makers. 

Pulse demonstration apparatus: a glass U-tube manometer for 
demonstrating fluid pressure is linked up with thoroughly flexible 
elastic tubing; an ordinary india-rubber enema makes a suitable 
pump. A simple lever resting on the tubing will illustrate the pulse. 

A larynx, hardened in spirits, then dissected out, may be pre- 
served as a permanent flexible specimen by immersion in strong 
glycerine. 

A dialyser for simple experiments on diffusion. 

Chemical thermometers. 

Essentials for experiments on salivary, gastric, and pancreatic 
digestion. (A water-bath to be kept at 40 C., and reagents, viz. 
HC1, 0-2 per cent; strong HNO 3 ; AmHO; NaHO, 5 per cent; very 
dilute H 2 SO 4 ; Millom's reagent; Fehling's solution; Na 2 CO 3 , i per 
cent. For gastric and pancreatic digestion, Benger's " liquor 
pepticus " and " liquor pancreaticus " provide the best supply of 
enzymes for the preparation of the digestive solutions.) 

(Bulky physiological material may be preserved in a large vessel 
containing formalin solution.) 



The Workshop 

All science teachers should make themselves familiar with 
the commoner tools used by carpenters and metal-workers. 
Moderate skill in most of tiie operations may be acquired with 
very little practice. A science teacher should be able to devise 
and make apparatus for simple experiments, to modify appa- 



422 SCIENCE TEACHING 

ratus, and to eFect simple repairs. He should be able tc ase 
the lathe and the few machines often found in the school 
workshop. If no machines are available, he should learn to 
use the bench drill (cramp and brace), the breast drill, and the 
stocks and dies. 

The following tools, &c., should be supplied for laboratory- 
workshop use: 

Drills, cold chisels, punches, files, a smith's vice, a J-lb. hammer, 
a ij-lb. hammer, pair of 9-in. shears, round pliers, flat-nose pliers, 
soldering iron, tinman's solder, zinc chloride, " fluxite ", rosin. 
Emery cloth, Nos. i, F, FF. Blue-black emery paper, No. o. A small 
anvil. 

Screws; terminals; insulated wire for coils; brass rod, strip, and 
sheet; copper sheet; zinc sheet. Get iron castings from the local 
foundry, and from the local blacksmith such wrought iron as may be 
necessary. 

The commoner carpenters' tools, and a small supply of hard 
and soft woods. 

Lacquers: colourless, pale gold, French gold. 

Cements: water-glass and lime cement, water-glass and Portland 
cement, cement for iron. 

Dips: bright dip for brass, matt or dead dip. 

Silvering mirrors: rather too difficult for amateurs to do well. 

Useful books are Shenstone's Glass-blowing, Threlfall's 
Laboratory Arts, Woollatt's Laboratory Arts. Much knowledge 
may be picked up by making friends with a village blacksmith, 
tinsmith, carpenter, and plumber. A day's initiation will go 
a long way. In a large town this kind of help is more 
difficult to obtain. 



CHAPTER XXXIX 

Science Libraries 

Such a multitude of books on science are now being pub- 
lished that it is exceedingly difficult to make a selection for the 
school library. Specialists in all departments of science are 



SCIENCE LIBRARIES 423 

writing, some who know )iow to write and some who do not. 
A writer may have a great name as a specialist in his own 
line, and yet when he attempts to write about his work he 
may fail to give a clear account of it. On the other hand, a 
writer possessing gifts of clear expression may write on a 
subject about which he knows very little; he may perhaps 
serve up a few tit-bits which will interest the multitude but 
which are useless for the serious consideration of people who 
wish to acquire exact and reasoned knowledge. How is the 
teacher to make a selection? He cannot read all the books 
published, even if he has access to a first-class library. Who is 
to guide him? 

" The survival of the fittest " applies to books as well as 
to living things. After a few years, books of little or no value 
die a natural death, though unfortunately they are not always 
cremated. The specific value of the survivors becomes gradually 
known, and selection is comparatively easy. The real difficulty 
is with the new books. Every science teacher desires to spend 
to advantage the usually small amount of money allotted annu- 
ally for the purchase of new science books, and there is always 
the danger of second-rate books being selected. 

Good sound copies of older books can usually be obtained 
second-hand. London contains dozens of well-known second- 
hand bookshops; Oxford and Cambridge come next, and some 
of the big provincial towns, especially the university towns, 
are a good third. There is no difficulty in building up a science 
library of older books, at a reasonable cost. 

But even experienced and well-read science teachers are 
glad to have the help of prepared lists of books for school 
science libraries, and, of such lists, the best is that compiled 
by the Joint Committee of the Science Masters' Association 
and the Association of Women Science Teachers, with supple- 
ments. These associations are, I believe, ever ready to give 
advice to inquirers, and all science teachers ought, by active 
membership, to support these exceedingly useful associations. 

The best reviews of new science books are to be found in 
Nature and in the School Science Review.* The former has 



424 SCIENCE TEACHING 

always been noted for its weighty reviews on new standard 
works of science, both British and foreign, and though many 
of the books are beyond the range of the work attempted in 
schools, they are just what the science teacher requires for 
building up his own private science library and for keeping his 
knowledge fresh. The School Science Review gives reviews by 
well-known science teachers who not only know their own 
subjects but who know what they are talking about from the 
point of view of class-room practice. I do not think I have ever 
read in its pages a review with which I disagreed. 

Nature also issues periodically a supplement giving a list 
of all recently published works in mathematics, science, and 
technology. With this in his hand, a science teacher visiting 
a science library like that, say, of Messrs. H. K. Lewis, can 
examine any particular new book at once. Sir Richard Gregory 
read a particularly useful paper on " Standards of Book Selec- 
tion in Science and Technology " at Cambridge in September, 
1927; it was reproduced in Nature, 8th October, 1927. 

It is, unfortunately, true that the majority of science books 
suitable for school use are written down to examination require- 
ments. In this country, writers do not care do not dare 
to ignore these requirements, or the books will not sell. Thus, 
apart from works of the popular type, books of a strikingly 
original and stimulating kind are comparatively rare. 

To compile a list of " best books " is to ask for trouble. 
Opinions necessarily differ, and this is all to the good. It 
would be a matter for regret if school libraries ever became 
standardized. Experienced teachers should compile lists for 
themselves. 

Do not forget foreign books. German books are usually 
sound though they are apt to be ponderous. French books are 
more lively, almost invariably interesting, with a freshness of 
presentation. Not all of the vast number of American books 
are equally good by any means, but not a few of them are really 
excellent; those issued by the University of Chicago Press ought 
to be known to all science teachers. 

Sonnenschein'j The Best Books is a particularly useful 



SCIENCE ^IBRARIES 425 

reference volume, though^ each edition is sown UUL of date, 
unfortunately. 

Keep an eye on the papers occasionally read at meetings 
of the learned societies and often reproduced in Nature-, also 
on lectures of the historical review type that are sometimes 
given by well-known men of science. Sir J. A. Ewing's lecture 
on A Century of Inventions, given before the Institute of Civil 
Engineers on 4th June, 1928, is a case in point. 

Here is a short supplementary list of books, historical and 
other, for general reading, some for the school library, some 
for the teacher's private library. 

1 . A Short History of Science, Sedgwick and Tyler. 

2. Introduction to the History of Science, W. Libby. 

3. Introduction to the History of Science, G. Sarton (Vol. I ready). 

4. Geschichte der Naturwissenschaften, Dannemann (the best). 

5. Babylonians and Assyrians, A. H. Sayce. 

6. History of Anthropology, A. C. Haddon. 

7. Historia Animalium, Aristotle (trs. by D. W. Thompson). 

8. The Works of Archimedes, T. L. Heath. 

9. History of the Inductive Sciences, W. Whewell. 

10. History of European Thought in the jgth Century, J. T. Merz. 

11. Discovery, Sir Richard Gregory. 

12. Pioneers of Science, Sir Oliver Lodge. 

13. Martyrs of Science, Sir David Brewster. 

14. A Short History of Mathematics, Ball. 

15. A History of Mathematics, Cajori. 

1 6. History of Greek Mathematics, Gow. 

17. Science of Mechanics, Mach. 

18. Astronomy, A. R. Hinks. 

19. Great Astronomers, Ball. 

20. Story of the Heavens, Ball. 

21. Problems of Cosmogony and Stellar Dynamics, Jeans. 

22. Lectures on Some Recent Advances in Physical Science, P. G. 

Tait. 

23. Recent Advances in Physical Science, W. C. D. Whetham. 

24. The New Physics, Haas. 

25. Problems of Modern Physics, Lorentz. 

26. Lectures on Theoretical ^hysics, Lorentz. 

27. Matter and Energy, Soddy. 

28. Radio-active Substances and their Relations, Rutherford. 

29. Atoms and Rays, Lodge. 



426 SCIENCE TEACHING 

30. Atomic Structures and Spectral Lines, Sommerfeld. 

3 1 . Alchemy and the Beginnings of Chemistry, Muir. 

32. History of Chemistry, Thorpe. 

33. Essays on Historical Chemistry, Thorpe. 

34. Progress of Scientific Chemistry in our own time, Tilden. 

35. A History of Chemical Theories and Laws, Muir. 

36. Industrial and Manufacturing Chemishj, Martin. 

37. Alembic Club Reprints. 

38. The Gases of the Atmosphere, Ramsay. 

39. A History of Botany, J. R. Green. 

40. Lectures on the History of Physiology in the lyth and i8th 

Centuries, Michael Foster. 

41. On the Movement of the Heart's Blood, Harvey. 

42. History and Scope of Zoology, Lankester. 

43. Darwinism, A. R, Wallace. 

44. Evolution in the Light of Modern Knowledge, Jeans and others, 

45. Darwin and Modern Science, Seward and others. 

46. Principles of Geology, Lyell. 

47. Founders of Geology, Geikie. 

48. Palaeontology, S winner ton. 

49. Grammar of Science, K. Pearson. 

50. Introduction to Science, Thomson. 

51. Method and Results, T. H. Huxley. 

52. Science and Hypothesis, Poincar. 

53. Bacon's Philosophical Works, Ellis and Spedding. 

54. Memoirs of Sir Isaac Newton, Brewster. 

55. Isaac Newton, Memorial Volume; ed. W. J. Greenstreet. 

56. John Dalton, Roscoe. 

57. Humphry Davy, Thorpe. 

58. Faraday as a Discoverer, Tyndall. 

59. Michael Faraday, S. P. Thompson. 

60. Life and Letters of Faraday, Bruce Jones. 

6 1 . Life and Letters of Charles Darwin, Francis Darwin. 

62. Darwin and after Dawrin, G. J. Romanes. 

63. Lord Kelvin , A. Grey. 

64. Life of Pasteur, Vallery-Radot. 

65. Pasteur and after Pasteur, Paget. 



APPENDIX 

QUESTIONNAIRES FOR PUPILS AND 
FOR TEACHERS 

A^QUESTIONNAIRE FOR BOYS LEAVING SCHOOL 

It would be reasonable to expect boys on leaving school 
to give intelligent answers to the following questions, which 
are not of the usual examination type. It does not, of course, 
follow that the necessary information will have been formally 
imparted during the science lessons. The boys will presumably 
have read up a good deal of science in addition to what they 
have read for examinations. 

1 . How could you estimate the number of flaps made in a second 
by the wings of a flying blue-bottle? 

2. Explain why the new moon is always seen in the west. 

3. Why will a clean needle float if placed gently on the surface of 
water? 

4. Why does an india-rubber ball bounce? 

5. What is the use of tall chimneys? 

6. Draw a diagram to show clearly the length of the shortest 
looking-glass you require in order that you may see the reflection of 
the whole length of your figure. 

7. What is a mirage? Why is it such a common phenomenon in 
the Soudan? : 

8. Explain what there is wonderful in the fact that the body 
temperature of all human beings in normal health is the same 

(98-4). 

9. When we think of some portion of the earth devoid of all forms 
of animal life, why must we necessarily think sf it as something abso- 
lutely dark and silent, despite a brilliantly shiniftg sun or violent 
thunderstorm? 

(E72) 427 29 



428 SCIENCE TEACHING 

10. If you were taken to the North Pole, how could you satisfy 
yourself that you were really there? Would the setting of the compass 
be affected? Could you still travel N., S., E., and W.? If not, why not? 

11. How is it that bees do not mix up pollen hopelessly c.s they 
pass from flower to flower? v 

12. The sudden flaring up of a particular star a few years ago 
seemed to point to a tremendous stellar catastrophe. Astronomers 
stated that the catastrophe must actually have taken place in the 
reign of Queen Elizabeth. On what grounds was such a statement 
made? 

13. Describe the manufacture of artificial silk. 

14. What do you know of the by-products of a gas-works? Are 
any of them valuable? Who made the discovery? 

15. How are tram rails welded together? What is the nature of the 
stuff used and what is the chemical action? Why is the welding 
necessary, considering that railway-rails are not treated similarly? 

1 6. Describe how the electric energy of a broadcasting station 
is transmitted to your receiving-set. Inasmuch as energy is radiated 
from the station, why have you to provide further energy for the 
working of your own valve set? 

17. A canal crosses over a road 30 feet wide by means of a bridge. 
A barge 16 feet long and weighing 20 tons passes along the canal. 
When the barge is over mid-bridge, what is the extra weight, if any, 
carried by the bridge? 

1 8. Explain exactly how the engine of a motor-car works. 

19. We think of the shape of rain-drops as spherical. Is there 
any ground for this? 

20. It is sometimes said that when a ship goes down the boilers 
" blow up ". Why is it extremely unlikely that this really happens? 
What gives rise to the idea that it does happen? What is the nature 
of an explosion? 



A QUESTIONNAIRE ON GENERAL SCIENCE 
FOR YOUNG SCIENCE TEACHERS 

It would also be reasonable to expect young science teachers, 
who are hoping to be promoted to the headship of a science 
department, to test their knowledge by such questions as the 
following: 

i. How do you account for Faraday 's extraordinary success as a 
physicist, seeing that he had no knowledge of mathematics? 



APPLNDIX 429 

: u. Was the electron discovered or invented? (16 you are uncertain, 
consult Professor Armstrong.) 

3. Discuss the future possibility of the transmutation of gold from 
base metals. 

4. Why are v^e quite certain that the common microscope will 
never be constructionally improved so far that we shall be able to see 
molecules and atoms? 

5. How far into the sun has it been estimated we can see? What is 
the evidence on which the estimate is based? 

6. A chisel is sharpened on a grindstone and then finished on an 
oilstone. There is a fundamental difference between the two processes. 
What is it? 

7. Justify the following statement: " A square mile of the most 
fertile soil can support with the solar heat it annually consumes only 
a definite number of human beings, which no art or science can in- 
crease." 

8. Describe your mental picture of a cyclone. Produce the evidence 
to show (i) the shape, (2) the movements, of the cyclonic mass of air 
as you have conceived it. 

9. How does a colour-blind person's view of the spectrum differ 
from that of a person of normal vision? 

10. What is the estimated age of the earth, as made by physicists 
and geologists, respectively? Do you attach more value to one estimate 
than to the other? If so, why? 

11. If the velocity of rotation of the earth were 17 times as great 
as it is now, what would be the consequence? Does the number 17 
agree with your conclusion? How do you make the calculation? 

12. What are the advantages of the modern steel girder and steel 
roof truss over the ancient stone arch and vault? Compare the ancient 
and modern methods of getting rid of lateral pressure in the spanning 
of large buildings and enclosed spaces. 

13. Do you consider that the estimates of stellar distances and 
electronic magnitudes correspond approximately with actual fact? 
What part of the available evidence i~ experimental and what part 
inferential? Is the latter evidence convincing? 

14. Do you favour the emission hypothesis or the wave hypothesis 
of light? If the former^ how do you explain interference? If the latter, 
how do you make the hypothesis square with the quantum hypothesis? 

15. Do you consider that the formaldehyde found in green leaves 
is an intermediate product in the manufacture of sugar from CO 2 and 
OH 2 , or a mere by-product resulting from the sugar disintegration? 
Why? What in your opinion is the source of the great amount of 
energy for converting CO 2 into sugar? Are 1 you satisfied that light 
alone is sufficient to provide it all? 



430 SCIENCE TEACHING 

1 6. If you were given the option, either to be bitten by a mosquito 
or to be stung by a wasp, which would you choose? Compare the toxic 
effects of the two. 

17. Did Sir Arthur Keith's British Association address on Evolu- 
tion strengthen your belief in the Evolutionary hypothesis? In your 
opinion, is the hypothesis now established on such a firm basis that 
it has passed into the region of strong probability? Are there any 
seriously weak links in the chain between the protozoan and the 
mammal? 

1 8. A compressed helical steel spring fits exactly into a cylindrical 
glass dish. Dilute H 2 SO 4 is poured into the dish, and the steel is 
dissolved. What has become of the potential energy stored in the 
spring? Are you sure'? What experiment can you devise to prove your 
statement? Is the experiment really practicable? 

19. It is generally assumed that the flexion lines on the palm of 
the hand have been induced by use. But they appear on the foetal 
hand, before the corresponding movements have begun. Do you 
infer from this that acquired characters may be inherited? 

20. Discuss with your classical colleagues the relative values, 
from the point of view of an intellectual training for citizenship, of 
classics and science (ignore the question of knowledge). Has science 
the advantage over classics, in any one particular? Has classics over 
science? Set out the facts and arguments, and try to get your judg- 
ment accepted by the Common Room. 



A QUESTIONNAIRE ON METHODS OF TEACHING 
FOR YOUNG SCIENCE TEACHERS 

It would also be reasonable to expect the same young 
science teachers to answer questions of the following type: 

i. Draft a working syllabus in Hydrostatics, with an historical 
bias, based on the work of Archimedes, Pascal, and Boyle. 

2,. Criticize the various makes of Boyle's Law apparatus in the 
market, from the point of view of demonstrati .ig the law clearly and 
convincingly to young pupils. 

3. You are asked to devise a switchboard for a new lecture-room. 
How would you rig it up in order that it might be of the maximum 
practical value to pupils receiving lessens in electricity? What instru- 
ments should it carry, ai?d why? 

4. In their book, First Principles of Chemistry^ Messrs. Dootson 
and Berry say that the Laws of Multiple and Reciprocal Proportions 



APPLNDIX 431 

ha,^ become obsolete. Criticize this statement, especially in regard to 
its bearing on the teaching of the theory of chemistry. 

5. At what stage in the teaching of science do you think that 
rigorously logical reasoning should be insisted on? 

6. Do you agree that the main principles of a subject of science 
are likely to be obscured if applications and illustrations are freely 
used? If so, what is y~ur remedy? 

7. What are " leading questions "? When is a science teacher 
justified in using them? 

8. As far as you can judge from books you have read and from 
opinions you may have heard expressed, do you think that science 
teach 's better now than it was a generation ago? If so, give precise 
reasc the opinion you hold. 

Germans, who have given at least as much attention to 

me' f science teaching as other leading nations have, are any- 

thi great believers in laboratory instruction for boys at schools. 

Ar Jrerman boys have at least as much knowledge, show at least 

a? intelligence, and have at least as firm a grasp of principles, 

& ^h boys. How does this fact affect your views concerning our 

i lethods of science teaching? 

Give instances of " verification " experiments that may be of 
What is your experience of boys " cooking " their experiments, 
.ch cases? 

1 1 . Are text-books in science necessary for forms below the Sixth? 
If so, precisely what part should such books play in the course of 
science taught? Should a boy give priority to what you teach him, 
or to what the book tells him? Why? 

12. Read through Professor Armstrong's book, and note down 
all the teaching principles which he advocates. Discuss these principles 
with your non-science colleagues. Now write down the pros and cons 
of the heuristic method. What do you think of the method? Are you 
going to adopt it or to reject it? Why? 

13. For a subject like " ^volution ", no practical work is possible. 
How will you ensure that the \/ork pttempted calls forth from the 
pupils an adequate mental effort? 

14. Writing to Nature, a distinguished chemist referred to a lec- 
ture on Electrons, given by Sir J. J. Thomson to the students at 
Girton College, Cambridge. He said: " Sir J. J. Thomson can thrill 
the young things at Girton with an account of the new shingled 
electron and its waved front." Apparently the distinguished chemist 
denies that University students reading for Honours in science should 
receive a lecture from a world-tamed physicist on a subject in which 
all the world is interested. What is your opfnion of his opinion? 

15. If there is one thing likely to shake the confidence of pupils 



432 SCIENCE VEAOTNG 

in their science teacher, it is his failure to make his experiments juc- 
cessful. But even in the hands of expert botanists, plant physiology 
experiments are apt to fail, particularly experiments on water-cul- 
tures. Repeated failures may induce the pupils to think either that 
the teacher does not know his work or that the experimental work is 
without value. Can you devise a scheme of apologetics to meet the 
case? 

1 6. Draw up a working syllabus in chemistry for the four years 
preceding the School Certificate examination, showing clearly when you 
would begin to teach the theory of the subject, how you would develop 
it step by step, and where and when. 

17. In a country school where very few pupils remai r the 
school certificate stage, what steps would you take to ens <n 
adequate course of elementary biology is included in t ace 
course? 

1 8. What course of reading would you advise for a Si} m, 
to make the boys keen to examine the foundations of an ice 
subject in which they are interested? 

19. Some years ago a science teacher, working single- I, 
was trying to extinguish the burning woodwork (pitch-pint 
fume cupboard which had been set on fire by a badly place 
draught, flame, when he was urgently called to a boy who had bi 
unconscious through the inhalation of chlorine. How would you _ 
coped with the double emergency? 

20. If you were Head of the science department in a large school, 
how would you organize the work necessary for the proper correction 
of the many hundreds of notebooks in use? What advice on the 
subject would you give to your colleagues? 



INDEX 



Abercrombie, 325. 

Aberration, 351. 

Abiogenesis, 249. 

Acceleration, 130. 

Accommodation and equipment, 405. 

Acquired characters, 231, 242. 

Actinotherapy, 232. 

/Ether, 148, 172. 

given up? 148. 
/Etherial radiation, 336. 
Agricultural Botany, 308. 
Agricultural chemistry, 164. 
Agriculture, ministry of, 197. 
Air and its Ways, The, 326. 
Alchemy, 380. 

Alembic Club Reprints, 44. 
Alexandria, 379. 

American comparative test of methods, 
30. 

men of science, 381. 

method, 29. 

topic method, 37, 135. 
Ampere, 140, 147. 
Aruesthesia, 275. 
Analysis of sound, 119. 
Anatomy, 184. 

comparative, 245. 
Ancient astronomy, 380. 
Andromeda, 372. 
Angstrom units, 336. 
Animal Biology, 258. 
Animal locomotion, 283. 
Animal Mysteries, 82. 
Animals, collections of, 214. 

comparative study, 210. 
Anticyclones, 112. 

Antiseptic and aseptic n^thods, 267. 

Antitoxins, 271. 

Apparatus and equipment, 416. 

Approach to botany, experimentally, 102. 

Approach to Teaching, 3. 

Aquarium Book, 82. 

Aquarium for schools, 80. ^ 

Archimedes, 32, 83, 122, 128, 379, 382. 

Aristotle, 14, 15, 379, 387. 

Armstrong, II. E., 20, 22, 27, 57, 177. 

Arrhenius, 175, 177. 



Ascaris for mitosis, 227. 

Ashford, 44, 45, 126. 

Association of Women Science Teachers, 

4', 423. 
Astronomy, 264. 

a more serious course, 287. 

ancient, 380. 

history of, 301. 

of the atom, 333. 

practical work, 285, 290. 

Sixth Form work, 291. 
usually taught, 284. 

with the naked eye, 302. 
Astrophysics, 302. 
Atmosphere, movements, 319. 

structure, 317. 
Atom, structure, 332. 
Atomic number, 348. 

Atomic Structure and Spectral Lines , 

348. 

Atoms and Rays, 348. 
Atvvood's machine, 126. 
Avogadro, 70, 167, 232, 382. 

Bacon, Francis, 14, 15, 244, 388. 

Roger, 32, 379. 
Bacteria, nomenclature, 270. 
Bacteriology, 184, 266. 

exercises in, 271. 

research work in, 273. 
Baird, 385. 

Baker, G.'W., 413- 

Balance rooms, 410. 

Baldwin, 400. 

Balfour, Lord, 388. 

Ball, Sir R., 301. 

Balmer, 377. 

Baly, Prof., 201. 

Barbarisms in scientific terminology, 109. 

Barrett, 162. 

Basel, 337. 

Bateson, 248. 

Beams, J. W., 375. 

Bedford, T. G., 57. 

Bcilstcinf 161. 

Bio-chemistry, 217, 218. 

Sixth Form*work in, 220. 



433 



434 



SCIENCE TEACHING 



Biogenesis, 249. 
Biological by-ways, 282. 

classification and terminology, 186, 
189. 

f instruction, main principles, 181. 
neglect of, Preface, 179. 

laboratories, 415. 

nomenclature, 188. 
Biologists and naturalists, 183. 
Biology, 179. 

a difficult subject, 182. 

as a group of allied studies, 184. 

experimental difficulties, 183. 

genealogical tree, 250. 

general, rather than botany, 72. 

in rural schools, 305. 
Biophors, 235. 

Birth, 224. 

Bjerknes, 322, 323. 

Blastula, 225. 

Board of Education Act, 276. 

Bohr's interpretation, 341. 

Books, second-hand, 223. 

supplementary list, 425. 

to read, and how, 42. 
Borradaile, 214. 

Bose, 203. 
Botany, 184, 190. 

as formerly taught, 70. 

by-ways, 196. 

drawings, 194. 

earlier work, 191. 

equipment, 420. 

experiments essential, 190. 

now a serious subject, 71. 

Sixth Form work, 192. 

syllabus, 102. 
Boulenger, 82. 
Bourne, 214. 
Boyle, 58, 122, 128. 
Bragg spectrometer, 155. 
Breakage of apparatus, 414. 
British Association meeting, 126. 

men of science, 381. 

Zoologists' Committee, 179. 
Broad, Prof., 390. 
Brodetsky, Prof., 354. 
Brown, S. E., 43, 45, 46. 
Budding and grafting, 195. 
Buffon, 185. 

Calendar, 301. 

Calvert, 43, 45. 

Cambridge Plant Breeding Institute, 

384- 

Capillarity, lesson on, 36. 
Carnot, 151, 152. 
Cartesian diver, 142. 
Catalysts, 174. 
Cavendish, 44, 140. 
Celestial movements, 288. 
Cellulose industries, 160. 
Centripetal and centrifugal, 129. 



Charles, Law of, 61, 173. 
Chaucer, 387. 

Chem cal action, neglected opportuni- 
ties for illustrating, 171. 

laboratories, 410, 

Philosophy, 173. 

terminology, 178. 
Chemistry, 156. 

agricultural, 164. 

as an art, 168. 

as a science, 168. 

equipment, 419. 

for Agricultural Students, 308. 

history of, 175. 

industries, 168. 

in rural schools, 305. 

in touch with the world around, 156. 

modern applications, 101. 

organic, 101, 158, 168. 

physical, 101. 

physics first, 25, 170. 

regrouping of topics, 162. 

syllabus, 92. 

teachers with special knowledge of, 

157- 

text-books, 176. 

theory, 70, 163. 

work, fundamental principles, 165. 
Chicago University Press, 424. 
Chromatin, 234, 239. 
Chromosomes, 234, 239, 249. 
Churches and science, 379. 
Classical headmaster's criticism, 21. 
Classification in biology, 186. 
Clausius, 151. 

Cleaning agents and operations, 311. 

Clifford, 122. 

Coal-tar products, 159. 

Cohen, 162. 

Colburn the calculator, 27. 

Colour Vision, 145. 

Combustion, 162. 

Combustion hoods, 411. 

Committee of British Zoologists, 179. 

Common cause of failure, 58. 

Comparative anatomy, 245. 

sizes, 377. 

Comparative Study of Animals, 214. 
Concentric method, 34. 
Concepts of Modern Physics, 122. 
Conservation of energy, matter, mass, 

130- 

Constantinesco, 142. 
Content of nc -mal science course, 66. 
Control experiments, 197. 
Coolidge tube, 155, 
Copernicus, 32. 

Correcting pupils' note-books, 116. 
Coulomb, 140. 

Co; rse of work too restricted, 67. 
Crayfish, experimental work, 208. 
Cross, W. E., 45, 145. 
Culture solutions, 198. 



INDEX 



35 



Cultures, bacteria, 268. 
Cui'.c, 147, 382. 
Curvature of continuum, 355. 
Cuvier, 185, 244. 
Cyclones, 322. 

Dakin, Prof., 204, 206, 211. 
Dalton, 164, 167. 
Dark ages, 402. 

rooms, 410. 

Darwin, 3, 44, 79, 183, 155, 223, 232, 
233. 235, 244, 247, 248, 259, 384. 

Darwin the older, 108. 

Dates to be learnt, 382. 

Dauntsey Agricultural School, 308. 

Davy, 44, 140, 149, 176. 

Defant, 326. 

Department of Scientific and Industrial 
Research, 384. 

Descartes, 244. 

Descent of man, 264. 

Design in Nature, 282. 

De Sitter, 376. 

Determinants, 235. 

Diagrams, 116. 

Digestion, 219. 

Dingle, II., 302. 

Directed reading, 78. 

Discontinuity, surfaces of, 321. 

Discovery, 25. 

or search? 20, 26. 

pseudo methods of, 39. 
Discovery, 425. 

Discovery and Invention, 177. 
Disease carriers, 269. 

theories of, 272. 
Disinfectants and antiseptics 275. 
Dissection, purpose of, 211. 
Domestic science, 308. 

Dootson and Berry, 44, 156, 176, 430. 

Drafting courses of instruction, 269. 

Drosophila Melanogaster, 241. 

Drugs, 274. 

Dumas, 162. 

Dunstan, 162. 

Durell, 350. 

DyestufTs, 160. 

Dymond, 308. 

Dynamics or statics first? 125. 

Ear, the, 217. 

Eclipse prediction, 301. 

Ecology, 185, 193. 

Economic uses of plants, .06. 

Economy of time in laboratory, 40, 77. 

Eddington, Prof., 302, 350. 

Educational claims of science teaching, 

9- 

pamphlets, 17, 90. 
Eggar, 45. QO, 127. 
Egyptians and Babylonians, 379. 
Einstein, 350, 351, 352, 363, 392, 394. 
Electric lighting and traction, 136, 137. 



Electrical instruments, 143, 418. 

units, 138. 
Electricity, 136. 

courses, present-day developments, 

137- 

Electromagnetic origin of matter, 372. 

Electron theory, scepticism about, 377. 

Elementary physical science for be- 
ginners, 86. 

Embryo, 224, 226. 

Embryology, 184, 223, 228, 245. 

basic facts to be taught, 224. 

human, 229. 

material and books, 229. 

practical work, 225. 

why it should be taught, 223. 
Encyclopcedia Britannica, 177, 203. 
Energy, 142, 345. 

of escape, 334. 
Engine, 149. 

Enzymes and ferments, 220, 221. 
Epigenesis, 232, 233. 
Equivalence, principle of, 355* 
Evaporated foods, 160. 
Evolution, 184, 193, 243, 380. 

and environment, 247. 

constancy of specific characters, 249. 

Darwinian theory, 243. 

difficulty of accepting hypothesis, 

257- 

evidence for, 245. 

factors, 247. 

suggested sequence of topfcs, 244. 

the great range of the subject, 243. 
Evolutionary lineage, examples of, 258. 
Ewing, 147, 425. 

Examiners' syllabuses and teachers' syl- 
labuses, 86. 

Excursions and rambles, 195. 
Experimental Embryology, 230. 
Experimental Proofs of Chemical Theory, 

.43, I73-. 

Extinct species, 256. 
Eye, the, 217. 

Faraday, 3, 39, 43, 44, 140, 176, 381 

384, 401. 

Faraday as a Discoverer, 140. 
Fi^er passers, 271. 
First aid in the laboratory, 177. 
Fison Memorial Lecture, 147. 
Fitzgerald, 351. 
Flatland analogy, 355. 
Flatters and Garnett, 230. 
Fleming, Prof., 45, 141. 
Fletcher, W. C., 45, 46, 126. 
Foetus, 224. 

Force, definition of, 128. 
Forecasting weather, 327. 
Formal training in science, its value, n. 

object of, 12. 

versus knowledge giving, 13. 

Formulae, 173. <* 



436 



SCIENCE TEACHING 



Formicarium for schools, 80. 

Fossils, 256, 257. 

Foster, Prof. M., 146, 216. 

and Balfour, 230. 

Four-dimensional continuum, 255. 

France, men of science, 381. 

Franklin, 140, 381. 

Fresnel, 146. 

Frog, experimental work, 207. 

Galen, 402. 

Galileo, 3, 32, 58, 122, 391. 

Galsworthy, 400. 

Galton, 112, 232, 236, 237. 

Galvani, 140. 

Ganong, Prof., 43, 47, 55. 

Gardiner, E. A., 43. 

Gardens, school, 80, 194. 

Garnett, W., 132. 

Gastrula, 225. 

Gay Lussac, 70, 167, 232, 382. 

Geddes, 326. 

Geikie, 32. 

Gemmules, 233, 235. 

Genealogical tree in biology, 250. 

General biology rather than botany, 72. 

Genes, 240. 

Genetics, 185. 

Geodesies, 356. 

Geographical distribution of species 246. 

Geology and Palaeontology, 253. 

as commonly taught, 253. 

eras, periods, epochs, 255. 

groups, systems, series, 255. 

outdoor work, 253. 

suggested topics for school courses, 

255- 

German method, 29. 
Germany, men of science, 381. 
Germinal continuity, 232, 234. 
Germination of seeds, 191. 
Germs, fear of, 275. 
Gilbert, 140. 

Girls, physical science necessary, 72. 
Girls' schools, 70. 
Glass-blowing, 422. 
Glazebrook, 46. 
Glazebrook and Shaw, 57, 142. 
Grafting and budding, 195. 
Grammar of Science, 122. 
Graphic statics, 126. 
Gravimetric analysis, 172. 

and volumetric work, 172. 
Gravitation, 356. 

and acceleration, 353. 

and electricity, 372. 

fields, 354. 

history of, 380. 

law of, 356, 357. 
Great and small, 373. 

workers, 380. 

Gregory, Sir R., 32, 43, 45, 302, 424, 



Grotthus, 175. 
Growth and Form, 282. 
Gue.icke, 122. 
Guillaume, 45. 

Haas, Prof., 376. 

Hadley, 43, 44, 45. 

Hagenbach, 387. 

Haldane and Huxley, 185, 258, 262 



Lord, no. 
Hall, Prof., 54. 

Sir A. D., 87. 
Halliburton, 215. 
Hansel, 44. 

Hare's apparatus, 128. 

Hart, 43, 45. 

Hartley, Prof., 45. 

Hayling Island Mosquito Station, 

3.84- 

Hearing, theory of, 143. 
Heart and arteries, 216. 
Heat, 134. 

apparatus, 418. 
Hellenic genius, 379. 
Helmholtz, 145, 146. 
Heredity, 180, 234. 

acquired characters, 231, 242. 

basic facts for pupil, 230. 

hypotheses, 231, 232, 236. 

main principles recognized, 238. 

the controversial question, 242. 

variations, 231, 248, 249. 
Herodotus, 202. 
Herschel, 119. 

Hertz, 122, 141. 

Heuristic method, 20, 22, 26, 28. 
Hexagonal symmetry, 283. 
Hill, 216. 
Histology, 184. 
Historical method, 31. 
History of a Candle, 43. 
History of Astronomy, 301. 

of chemistry, 174, 380. 

of science, 378. 

-- why it should be taught, 
378. 

of steam, 380. 

of textiles, 380. 
Hittorf, 175. 

van t'Hoff, 175. 

Hofmann, 162. 

Holland, mei, of science, 382. 

Holmyard, 43, 44, 45, 46, 52, 156, 162, 

172, 173, 174, 177. 
Honda, 148. 
Hooton, 44, 45. 
Hormones, 220. 
Human embryology, 229. 

origins, 265. 

physiology, 215. 
-- equipment for, 421. 



INIJEX 



437 



Mur in embryology, practical work 
thirty years ago, 215. t 

topics for special consideration, 

216. 

Hutchinson, 44. 
Huxley* T. H., 12, 33, 39. 43. iO9 185, 

214. 

Huygens, 122, 146. 
Hybridization, 237. 
Hydrogen spectra series, ^^9. 
Hydrostatics, 127. 
Hygiene, 276. 

for girls, 72. 

foundations of, 281. 

practical work, 280. 

teaching advisable, 278. 
Hygienic bacteriology, 268. 
Hymans, 208, 211. 
Hypothesis, 390. 

succeeding hypothesis, 154. 
Hypotheses discarded, 391. 

of light, 146. 

Ids, 235. 

Immunity, 274. 

Inadequate laboratory directions, 171. 

Indicator diagrams, 150. 

Indicators, 150. 

Induction and hypothesis, 389. 

by beginners, 38. 
Industrial processes, 160. 
Inference, 398. 
Influenza, 274. 

Informal physics and chemistry for 

beginners, 85. 

Institute of Civil Engineers, 425. 
Intellectual training, relative values of 

different subjects, 9. 
Internal Constitution of Stars, 302. 
Introduction to experimental science, 82. 
Invertebrate paheontology, 258. 
Investigators of mechanics, 122. 
Iron and steel, 380. 
Isentropic surfaces, 320. 
Italy, men of science, 382. 

James Allen School Gardens, 194. 
Jeans, Sir ]., 302. 
Joule, 149, 151. 
Jude, 44. 

Kala Azar, 274. 
Keeble, 47. 
Kelvin, 140, 151, 250. 
Kempson, 44. 
Kepler, 32, 350. 
Kew Gardens, 81, 386. 
Kinematics, 125. 
Kinetics, 125. 
Kirchhoff, 32. 

Knowledge necessary for science 
teachers, 5. 

versus training, 13. 



A^vjCh, 266, Zww, JWX. 

Kolbe, 175. % 

Laboratories, 408. 
Laboratory Art, 422. 
Laboratory assistant, 412. 

bottle washer, 412. 

economy of time, 40. 

equipment, 407, 408. 

first aid, 177. 

instructions, 29, 47. 

inadequate, 171. 

not satisfactory, 47. 

satisfactory, 52. 

notes, 78. 

ritual, n. 

procedure in zoology, 212. 
Lamarck, 185, 232, 233, 234, 247. 
Langevin, 148. 

Langlois, Prof., 387. 
Lankester, Sir R., 58. 
Laplace, 381. 
Large numbers, 374. 
Larmor, Prof., 393. 
Latter, O. H., 90, 214. 
Laue, 155, 336. 
Laundering, 159. 
Law of Charles, 61, 173. 

of Gay Lussac, 70. 
Laws of motion, 125. 

Lecture room and laboratory. 28. 

charts, 414. 

versus laboratory, 30. 

work, 28. 

rooms, 409. 
Lectures and Essays, 122. 
Lectures versus lessons, 17. 

in Sixth Form, 73, 75. 
Leibniz, 244. 
Leonardo, 122. 
Lempfert, 326. 

Lesson on capillarity, 36. 

on rainbow, 34. 

on X-rays, 154. 
Lewis, H. K., 424. 
Libraries, 422. 
Life, origin of, 250. 
Light, 135. 

^apparatus, 417. 

hypotheses, 146. 

refraction, 144. 

structure, 147. 
Linnaeus, 135, 244. 
Lister, 266, 267. 

Institute, 267. 
Living Machinery, 216. 
Lockyer, 301. 
Lodge, 141, 348, 393. 
Logarithmic spiral, 283. 

Logical or psychological order? 174. 
London Oay T. C., 41. 
Lorentz, 141, 351, 352. 
Lower Form srience, 79. 



438 



SCIENCE TEACHING 



Lubbock, 58, 79. 
Lucretius, 108. 
Lulham, 214. 
Lull, 230, 258. 
Lungs, 217. 
Luton, 157. 

M'Curdy, G. C., 265. 

Mach, 45, 121, 393. 

Magnetism, theories, 147. 

Man, descent of, 264. 

Manual of Elementary Zoology , 264. 

of Meteorology, 327. 
Marconi, 141. 
Margules, 321. 

Marks of a successful teacher, 3. 

Marlborough, 379. 

Marshall, 214. 

Marshall and Hurst, 214. 

Martin, 146. 

Mass and weight, 132. 

Mathematical Gazette, 354. 

Mathematical reasoning, 393. 

Matter and Motion, 45. 

Maturation, 235. 

Maxwell, 45, 140, 141 145, 146, i47> 

372, 394- 

Mechanical inventions, 127. 
Mechanics, 45, 77, 119- 

a branch of physics, 121. 

and mechanism, 123. 

apparatus, 416. 

formerly known as mixed mathe- 

matics, 121. 

historical treatment, 122. 

inductive teaching, 123. 

in rural schools, 304. 

investigators, 122. 

knowledge essential, 121. 

proofs, 126. 

stage one, 123. 

stage two, 123. 

successful teachers of, 121. 

why included in school work, 1 19. 
Mediae valism, 32. 

Mediaeval science, 379. 
Medical Research Council, 385. 
Mendel, 185, 232, 236, 237, 238, 243, 

248, 382. 
Mendeleeff, 382. 
Men of the Old Stone Age, 265. 
Mercury bench, 414. 

orbit of, 357. 
Metchnikoff, 274. 
Meteorology, 317. 

teaching of, 324. 
Methods, 14. 

general remarks, 38. 

should be original, 42. 

of by-gone ages, 14. 

of forty years ago, 17. 
Meyer, Victor, 162. 
Miall, 79. 



Michelson-Morley experiment, 3-. 

Microscope, 193, 212. 

Middle Ages, 387, 390. 

Mill, J. S., 388. 

Miller, 44. 

Milton, 387. 

Ministry of Agriculture, 197. 

Mistakes by pupi.s should be recorded, 

Mitosis, 227, 241. 

ascaris for, 227. 

" Mixed " mathematics, 121. 
Modern applications of chemistry, 
101. 

astronomy pioneers, 380. 

Astrophysics, 302. 
Modes of Locomotion, 283. 
Molisch, 203. 

Moore, 201. 
Morgan, 241. 
Morphology, 184. 
Moseley, 47. 
Mullock, 283. 

Mutations and diminished vital energy, 
248. 

Napoleon, 379. 

National Physical Laboratory, 68, 384. 

Natural History Museum, 81, 214, 258. 

selection, 247. 
Naturalist at the Zoo, The, 82. 
Naturalists and biologists, 183. 
Nature, 13, 112, 175, 203, 222, 223, 331, 

379, 414, 423, 425. 
Nature study, 66, 79, 80, 179. 
Nebulae, 296. 
Neglect of biological teaching, Preface, 

179. 

Nerve regeneration, 218. 
New educational prophets, 17. 
New Physics, The, 376. 
Newcomen, 149. 
Newth, 45, 46, 173. 
Newton, 3, 32, 44, 122, 123, 146, 301, 

35> 356, 381, 382, 384, 392, 394. 
Nomenclature in biology, 188. 
Non-specialist Sixths, 75. 
Normal physics course, 134. 

science course, 66. 
Note-making and note-taking, 113. 
Notes must be original, 1 14. 
Nunn, Prof., 41, 350. 
Nutrition of animals, 206. 

Observation visits, 70. 

Observatory, the school, 415. 

Oelschlager and Moss, 152. 

(Epinus, 140. 

Oersted, 140, 382. 

Ohm, 140. 

Oldham, 190. 

Opticks, 44, 384. 

Orderly procedure in teaching, 40. 



INDEX 



439 



Orgf-ic chemistry, 101, 158, 168. 
practical work, 161. 

evolution, 230, 258. 

forms, sizes of, 283. 

molecule, characteristic group, 158. 
Osborn, Prof., 265. 

Osmosis, 103. 
Ostwald, 175. 
Oundle, 308. 

Out-of-date knowledge, 6. 
Owen, 185. 

Paget, Sir J., 217. 
Palaeontology, 184, 245, 253. 

conditions of entombment, 256. 

varying composition of fossil skele- 

ton, 256. 

why knowledge necessary, 255. 
Palmerston, 379. 

Paludina, 258. 

Pangenesis, 232, 233. 

Paragraphing in note-making, 116. 

Pascal, 32, 58, 122, 128. 

Pasteur, 185, 249, 266, 267, 273, 381. 

Pathologic bacteriology, 268. 

Pearson, Karl, 122, 232, 237. 

Peddie, 145. 

Percival, 308. 

Perfumes, 160. 

Periodic Law, 100, 101, 334, 348. 

Personalties of great workers, 380. 

Pests and pest controls, 275. 

Pettigrew, 282. 

Pfeffer, 175. 

Ph.D. degree, 161. 

Philip, 177. 

Philosophic foundations of science, 

386. 

Philosophy, first notions, 386. 
Photosynthesis, 104, 200. 
Phyla, the principal should be known, 

188. 

Phyllotaxis, 283. 
Physical chemistry, 101. 
practical work, 161. 

laboratories, 413. 

science necessary for girls, 72. 
Physics, 134, 304. 

development of subject, 134. 

in chemistry experimentation, 169. 

modern tendencies, 153. 

must precede chemistry, 170. 

necessary for biologists, 74. 

normal course, 134. 

weak, connotes weak science, 74- 

wider course necessary, 140. 
Physiography, 81. 
Physiology, 184. 

human, 215. 
~ plant, 193. 

Pioneers of astronomy, 380. 
Pithecanthropus , 265. 
Planck, 346. 



F)ant ecology, 106. 

physiology, 193) 
Plants, economic use of, 107. 
Plasticine models in embryology, 226. 
Plato's method, 14, 15. 

Poisonous plants, 196, 197. 

Poisson, 140, 147. 

" Popular " science, 110. 

Port Sunlight, 157. 

Pound and poundal, 132. 

Poynting, 45. 

Poynting and Thomson, 46. 

Practical work in organic and physical 

chemistry, 161. 

Preformationist hypothesis, 232. 
Preparation of teaching syllabuses, 91. 

rooms, 410. 

Present-day tendencies in science teach- 
ing, 36. 

Priestley, 44. 

Prime Minister's Science Committee's 
Report, 75, 179. 

Principle of equivalence, 355. . 

Principles of science teaching, I. 

Proctor, 301. 

Proofs, in mechanics, 126. 

non-demonstrable, 394. 
Prophets, new educational, 17. 
Protein digestion, 220. 
Proteins, 312. 

investigation difficulty, 219. 

Pseudo method of discovery, ^39. 

Psychical research, 395. 

Ptolemy, 32. 

Pulse, 216. 

Pupils' note-book, 116. 

Qualitative analysis, 18, 19, ipi, 172. 
Quantitative experiments taking a long 

time, 69. 
Questionnaires for pupils and teachers, 

427-32. 

Radiation, 293. 
Radioacticity, 164, 334. 
Rainbow, lesson on, 34. 
Rambles and excursions, 195. 
Ramsay, Prof., 43, 173. 
Rc.iiarium for schools, 80. 
Rankin, 151. 
Reading, directed, 78. 

of original records, 78. 

versus weighing, 78. 
Recapitulation theory of development, 

228. 

Recording mistakes, 39. 
Records of laboratory work, 113. 
Rectification of alternating currents 

413- 

Refraction of light, 144. 
Reguli Pkilosophandi, 123. 
Reign of Relativity, no. 
Relative motiotf, 287. 



440 



SCIENCE TEACHING 



Relativity, 349. 

general theory, 3^3. 

of simultaneity, 357. 

problems unsolved, 372. 

special theory, 352. 
Remsen, 19. 

Report on Science Teaching (ed. Latter), 

90. 
Research, 383. 

by science teachers, 8. 

its significance and importance, 383. 
Respiration, 104, 198. 

Rice, 350. 

Richelieu, 379. 

Ritual of the laboratory, n. 

Ritz law, 342, 347. 

Rival hypotheses of light, 146. 

Rogers, 177. 

Roman decline, 275. 

technical excellence, 379. 
Romance of Modern Chemistry, 177. 
Rontgen, 155. 

Roscoe, Sir H., 20, 156. 

Roscoe and Ward, 3. 

Rothamsted Experimental Station, 308, 

384. 

Rowlands grating, 124. 

Royal Institution Lectures, 43, 147. 

Rubber and gums, 160. 

Rumford, 149. 

Rural schools, Board of Education Re- 
ports, 308. 

science courses, 303. 

science in, 302, 306. 

Sixth Form work, 308. 

Russell, J. B., 43, 45, 173. 

Rutherford, Sir E., 154, 335. 

Rydberg, 338, 347. 

Safety in Mines Research Board, 384, 

385- 

Safety Lamp, The, 44. 
School gardens, 80, 194. 
School Science Review, 41, 423. 
School World, 45, 58, 126. 
Schwann, 273. 
Science and Art Department, 276. 

and humanism, 400. 

and the modern world, 392. 

as a means of culture, 10. 

committee's report, 75. 

course to School Certificate stage, 66. 

degrees, 4. 

for All, 89. 

history of, 378. 

of, why it should be taught, 378. 

in rural schools, 302. 

libraries, 422. 

Master's Association, 41, 423. 
Library catalogue, 79, 308. 

teachers as teachers of English, 107. 

knowledge and training, 3, 5. 

training, 7. 



Science teaching, criticized by a Head- 
master, 21. 

educational claim, 9. 

present-day tendencies, 36. 

principles, r. 

since 1867, 15. 

Scientific Method, 398. 

Scientific terms loosely used, 112. 

" Scientist ", 112. 

Search or d.'/covery? 20, 26. 

Secret Remedies, 281. 

Seed germination, 191. 

Self-training, 41. 

Seventeenth-century workers, 391. 

Shafer, Sir E. S., 215. 

Shakespeare, 379, 387. 

Shaw, Sir N., 320, 326. 

Sheffield, 157. 

Shenstone, 43, 46, 156, 422. 

Shumway, 230. 

Simplicity of expression in science 
teaching, 109. 

Simpson, G. C., 326. 

Simultaneity, criterion of, 353. 

Sixth Form, exacting work necessary, 
76. 

lectures, 73. 

non-specialists, 75. 

science, 72. 

work, critics of, 329. 

extended considerations, 327- 

high standard necessary, 74. 

in bio-chemistry, 320. 

Small and great, 373. 

Smith, Prof. Alexander, 43, 44, 46, 53, 
92, 156. 

Smith and Hale, 53. 

and Hall, 43. 

Snags in botany teaching, 197. 

in chemistry teaching, 169. 

in mechanics teaching, 128. 

in physics teaching, 143. 
Solar spectra, 294. 

system, birth of, 300. 
Sommerfeld, 348. 
Sound, 135. 

analysis, of 119. 

apparatus, 417. 
Specialization in Sixth Form, 72. 
Species, 244, 245, 246. 

and their origin, 244. 

defined by type, 187. 

geographical distribution, 246. 

not fixed, 187. 
Spectroscope, 292. 
Spectrum analysis, 292. 
Spinoza, 244. 

Stallo, 122. 
Stalling, Prof., 216, 
Stars, birth of, 299. 

sizes of, 295. 

temperature and energy of, 296. 
Statics or dynamics first? 125. 



INDEX 



441 



Stet"y-engine, 149. 

history of, 380. 
Stellar spectra, 294. 

universe, size of, 372. 
Stevinus, 32, Jk2. 

Steward and Gee, 46, 57, 143. 

Stoke, 157. 

Storage cupboards, 4*4- 

Stratograpnical charts, 259-62. 

Stratosphere, 317. 

Structure and size, 282. 

Struggle for existence, 247. 

Successful science teachers, marks of, 3. 

Summer courses for teachers, 42. 

Sun, 300. 

Supplementary list of books, 425. 

Survival of the fittest, 247. 

Sweden, men of science, 382. 

Syllabuses and schedules of work, 86. 

Teachers of mechanics, 121. 

with special knowledge of chemistry, 

157- 

Teachers' syllabuses and examiners' 
syllabuses, 86. 

Teaching Botanist, The, 43, 45. 

Teaching of Scientific Method, 57. 

Teaching syllabus in chemistry, 92. 

preparation of, 91. 

Technical Electricity, 44. 

Technical terminology, how far de- 
sirable, 107. 

Telegraphy, 380. 

and telephony, 139. 
Terminology, barbarisms, 109. 

biological, 186, 189. 
~ in chemistry, 178. 
Terrarium for schools, 80. 
Text-books in chemistry, 176. 
Textiles, 380. 

Theology, 397. 

Theory of chemistry, 70. 

of relativity, 350. 
Thermodynamics, First Law, 149. 

Second Law, 151. 
Thompson, Prof. D'Arcy, 282. 

J. Arthur, 204, 211. 

Sylvanus, 34, 44. 

Thomson, Sir J. J., 46, 147, 335. 393- 
Thorpe, Prof., 45, 173. 

Threlfall, 422. 
Tilden, 73, 177. 
Tillyard, 384. 
Time allowance, 76. 

lost in laboratory, * , 

through overlapping of subjects, 

Times Educational Supplement, So. 

Todhunter, 45, 83. 

Topic method in America, 37, 135. 

Torricelli, 58, 122. 

Toxins, 271. 

Toys in illustration of principles, 142. 



'Framing of science teachers, 7, 41. 
Tropopause, 318^ 
Troposphere, 317, 319. 
Tyndall, 39, 45, 58, 249, 267. 

Ultramicroscope, 270. 

Units, 132, 138. 

University degrees in science, 4. 

University notes used for teaching, 5. 

Untidy laboratories, 412. 

Valency, 100, 168. 

Variation in species, 231, 248, 249. 

Vassall, 90. 

Vault of Heaven, 302. 

Vegetable Mould and Earthworms, 44, 79> 

384- 

Vertebrate Embryology, 230. 
Vestigial organs, 246. 
Vickers, 142. 
Vitamins, 220, 221. 
Vivaria for schools, 80. 
Voigt, 147. 
Volta, 140. 

Wager, H., 203. 

Wallace, 183, 185. 

Ward and Roscoe, 3. 

Wasp, external anatomy, 209. 

Water divining, 395. 

W T atson, Prof., 45. 

Watt, 149. . 

Wave-lengths and frequencies, 293. 

motion, 141, 351. 
Waves and Ripples, 45. 

Weak physics connotes weak science, 

74- 

Weather forecasting, 317. 
Weber, 147. 
Weight and mass, 132. 
Weismann, 185, 232, 234, 238, 240, 

248. 

Weiss, 148. 
Wells, 127. 

Wetter und Wettervorhersage, 326. 
White, Gilbert, 44, 79. 
Whitehead, Prof., 392. 
Willings, 43, 45, 46. 
Wilson, Canon, 15, 16. 

C. R.,335- 

Wireless, 139. 
Wolff, 232. 
Wood, 258. 
Woolaston, 140. 
Woollatt, 422. 
Wordsworth, 109. 
Work before twelve, 66. 
Workshop equipment, 421. 
World lines, 356. 
Wright, Lewis, 45. 
Writing of Clear English, 58. 
Writing of descriptions, 85. 
Written notejj, form of, 115. 



442 



SCIENCE TEACHING 



X-ray methods, 164. 
X-rays, '163. 

Young, 146. 

Young-Helmholtz-Maxwell hypothesis, 
145. 

Zoological Gardens, 87, 214, 386. 
Zoologists, Committee of, 179. 



Zoology, 184, 204. 

early observational work, 207. 

equipment, 420. 

function rather than form, 204. 

further work, 211. 

in rural schools, 306. 

laboratory work and procedure, 212.. 

study, comparison the essence of, 2 1 1 ,. 
Zygote, 239, 241.